public class TableId {
    private final int tableId;

    @Override
    public boolean equals(Object obj) {...}

    @Override
    public int hashCode() {...}
}

public class GraphNode {
    public final Stage<?> stage;
    public final TableId[] estimatorInputs;
    public final TableId[] algoOpInputs;
    public final TableId[] outputs;
}

/**
 * A Graph acts as an Estimator. A Graph consists of a DAG of stages, each of which could be an
 * Estimator, Model, Transformer or AlgoOperator. When `Graph::fit` is called, the stages are
 * executed in a topologically-sorted order. If a stage is an Estimator, its `Estimator::fit` method
 * will be called on the input tables (from the input edges) to fit a Model. Then the Model will be
 * used to transform the input tables and produce output tables to the output edges. If a stage is
 * an AlgoOperator, its `AlgoOperator::transform` method will be called on the input tables and
 * produce output tables to the output edges. The GraphModel fitted from a Graph consists of the
 * fitted Models and AlgoOperators, corresponding to the Graph's stages.
 */
@PublicEvolving
public final class Graph implements Estimator<Graph, GraphModel> {
    public Graph(List<GraphNode> nodes, TableId[] estimatorInputIds, TableId[] algoOpInputs, TableId[] outputs, TableId[] inputModelData, TableId[] outputModelData) {...}

    @Override
    public GraphModel fit(Table... inputs) {...}

    @Override
    public void save(String path) throws IOException {...}

    @Override
    public static Graph load(StreamTableEnvironment tEnv, String path) throws IOException {...}
}

/**
 * A GraphModel acts as a Model. A GraphModel consists of a DAG of stages, each of which could be an
 * Estimator, Model, Transformer or AlgoOperators. When `GraphModel::transform` is called, the
 * stages are executed in a topologically-sorted order. When a stage is executed, its
 * `AlgoOperator::transform` method will be called on the input tables (from the input edges) and
 * produce output tables to the output edges.
 */
public final class GraphModel implements Model<GraphModel> {

    public GraphModel(List<GraphNode> nodes, TableId[] inputIds, TableId[] outputIds, TableId[] inputModelData, TableId[] outputModelData) {...}

    @Override
    public Table[] transform(Table... inputTables) {...}

    @Override
    public void setModelData(Table... inputs) {...}

    @Override
    public Table[] getModelData() {...}

    @Override
    public void save(String path) throws IOException {...}

    public static GraphModel load(StreamTableEnvironment tEnv, String path) throws IOException {...}
}

/**
 * A GraphBuilder provides APIs to build Estimator/Model/AlgoOperator from a DAG of stages, each of
 * which could be an Estimator, Model, Transformer or AlgoOperator.
 */
@PublicEvolving
public final class GraphBuilder {     

    /**
     * Specifies the loose upper bound of the number of output tables that can be returned by the
     * Model::getModelData() and AlgoOperator::transform() methods, for any stage involved in this
     * Graph.
     *
     * <p>The default upper bound is 20.
     */
    public GraphBuilder setMaxOutputTableNum(int maxOutputLength) {...}

    /**
     * Creates a TableId associated with this GraphBuilder. It can be used to specify the passing of
     * tables between stages, as well as the input/output tables of the Graph/GraphModel generated
     * by this builder.
     *
     * @return A TableId.
     */
    public TableId createTableId() {...}

    /**
     * Adds an AlgoOperator in the graph.
     *
     * <p>When the graph runs as Estimator, the transform() of the given AlgoOperator would be
     * invoked with the given inputs. Then when the GraphModel fitted by this graph runs, the
     * transform() of the given AlgoOperator would be invoked with the given inputs.
     *
     * <p>When the graph runs as AlgoOperator or Model, the transform() of the given AlgoOperator
     * would be invoked with the given inputs.
     *
     * <p>NOTE: the number of the returned TableIds does not represent the actual number of Tables
     * outputted by transform(). This number could be configured using {@link
     * #setMaxOutputTableNum(int)}. Users should make sure that this number >= the actual number of
     * Tables outputted by transform().
     *
     * @param algoOp An AlgoOperator instance.
     * @param inputs A list of TableIds which represents inputs to transform() of the given
     *     AlgoOperator.
     * @return A list of TableIds which represents the outputs of transform() of the given
     *     AlgoOperator.
     */
    public TableId[] addAlgoOperator(AlgoOperator<?> algoOp, TableId... inputs) {...}

    /**
     * Adds an Estimator in the graph.
     *
     * <p>When the graph runs as Estimator, the fit() of the given Estimator would be invoked with
     * the given inputs. Then when the GraphModel fitted by this graph runs, the transform() of the
     * Model fitted by the given Estimator would be invoked with the given inputs.
     *
     * <p>When the graph runs as AlgoOperator or Model, the fit() of the given Estimator would be
     * invoked with the given inputs, then the transform() of the Model fitted by the given
     * Estimator would be invoked with the given inputs.
     *
     * <p>NOTE: the number of the returned TableIds does not represent the actual number of Tables
     * outputted by transform(). This number could be configured using {@link
     * #setMaxOutputTableNum(int)}. Users should make sure that this number >= the actual number of
     * Tables outputted by transform().
     *
     * @param estimator An Estimator instance.
     * @param inputs A list of TableIds which represents inputs to fit() of the given Estimator as
     *     well as inputs to transform() of the Model fitted by the given Estimator.
     * @return A list of TableIds which represents the outputs of transform() of the Model fitted by
     *     the given Estimator.
     */
    public TableId[] addEstimator(Estimator<?, ?> estimator, TableId... inputs) {...}

    /**
     * Adds an Estimator in the graph.
     *
     * <p>When the graph runs as Estimator, the fit() of the given Estimator would be invoked with
     * estimatorInputs. Then when the GraphModel fitted by this graph runs, the transform() of the
     * Model fitted by the given Estimator would be invoked with modelInputs.
     *
     * <p>When the graph runs as AlgoOperator or Model, the fit() of the given Estimator would be
     * invoked with estimatorInputs, then the transform() of the Model fitted by the given Estimator
     * would be invoked with modelInputs.
     *
     * <p>NOTE: the number of the returned TableIds does not represent the actual number of Tables
     * outputted by transform(). This number could be configured using {@link
     * #setMaxOutputTableNum(int)}. Users should make sure that this number >= the actual number of
     * Tables outputted by transform().
     *
     * @param estimator An Estimator instance.
     * @param estimatorInputs A list of TableIds which represents inputs to fit() of the given
     *     Estimator.
     * @param modelInputs A list of TableIds which represents inputs to transform() of the Model
     *     fitted by the given Estimator.
     * @return A list of TableIds which represents the outputs of transform() of the Model fitted by
     *     the given Estimator.
     */
    public TableId[] addEstimator(
            Estimator<?, ?> estimator, TableId[] estimatorInputs, TableId[] modelInputs) {...}

    /**
     * When the graph runs as Estimator, it first generates a GraphModel that contains the Model
     * fitted by the given Estimator. Then when this GraphModel runs, the setModelData() of the
     * fitted Model would be invoked with the given inputs before its transform() is invoked.
     *
     * <p>When the graph runs as AlgoOperator or Model, the setModelData() of the Model fitted by
     * the given Estimator would be invoked with the given inputs before its transform() is invoked.
     *
     * @param estimator An Estimator instance.
     * @param inputs A list of TableIds which represents inputs to setModelData() of the Model
     *     fitted by the given Estimator.
     */
    public void setModelDataOnEstimator(Estimator<?, ?> estimator, TableId... inputs) {...}

    /**
     * When the graph runs as Estimator, the setModelData() of the given Model would be invoked with
     * the given inputs before its transform() is invoked. Then when the GraphModel fitted by this
     * graph runs, the setModelData() of the given Model would be invoked with the given inputs.
     *
     * <p>When the graph runs as AlgoOperator or Model, the setModelData() of the given Model would
     * be invoked with the given inputs before its transform() is invoked.
     *
     * @param model A Model instance.
     * @param inputs A list of TableIds which represents inputs to setModelData() of the given
     *     Model.
     */
    public void setModelDataOnModel(Model<?> model, TableId... inputs) {...}

    /**
     * When the graph runs as Estimator, it first generates a GraphModel that contains the Model
     * fitted by the given Estimator. Then when this GraphModel runs, the getModelData() of the
     * fitted Model would be invoked.
     *
     * <p>When the graph runs as AlgoOperator or Model, the getModelData() of the Model fitted by
     * the given Estimator would be invoked.
     *
     * <p>NOTE: the number of the returned TableIds does not represent the actual number of Tables
     * outputted by getModelData(). This number could be configured using {@link
     * #setMaxOutputTableNum(int)}. Users should make sure that this number >= the actual number of
     * Tables outputted by getModelData().
     *
     * @param estimator An Estimator instance.
     * @return A list of TableIds which represents the outputs of getModelData() of the Model fitted
     *     by the given Estimator.
     */
    public TableId[] getModelDataFromEstimator(Estimator<?, ?> estimator

/**
 * A Graph acts as an Estimator. A Graph consists of a DAG of stages, each of which could be an
 * Estimator, Model, Transformer or AlgoOperator. When `Graph::fit` is called, the stages are
 * executed in a topologically-sorted order. If a stage is an Estimator, its `Estimator::fit` method
 * will be called on the input tables (from the input edges) to fit a Model. Then the Model will be
 * used to transform the input tables and produce output tables to the output edges. If a stage is
 * an AlgoOperator, its `AlgoOperator::transform` method will be called on the input tables and
 * produce output tables to the output edges. The GraphModel fitted from a Graph consists of the
 * fitted Models and AlgoOperators, corresponding to the Graph's stages.
 */
@PublicEvolving
public final class Graph implements Estimator<Graph, GraphModel> {
    public Graph(List<GraphNode> nodes, TableId[] estimatorInputIds, TableId[] modelInputs, TableId[] outputs, TableId[] inputModelData, TableId[] outputModelData) {...}

    @Override
    public GraphModel fit(Table... inputs) {...}

    @Override/**
     public void save(String path) throws IOException {...}

    @Override
    public static Graph load(String path) throws IOException {...}
}

/**
 * A GraphModel acts as a Model. A GraphModel consists of a DAG of stages, each of which could be a
 * Model, Transformer or AlgoOperators. When `GraphModel::transform` is called, the stages are
 * executed in a topologically-sorted order. When a stage is executed, its `AlgoOperator::transform`
 * method will be called on the input tables (from the input edges) and produce output tables to the
 * output edges.
 */
public final class GraphModel implements Model<GraphModel> {

    public GraphModel(List<GraphNode> nodes, TableId[] inputIds, TableId[] outputIds, TableId[] inputModelData, TableId[] outputModelData) {...}

    @Override
    public Table[] transform(Table... inputTables) {...}

    @Override
    public void setModelData(Table... inputs) {...}

    @Override
    public Table[] getModelData() {...}

    @Override
    public void save(String path) throws IOException {...}

    public static GraphModel load(String path) throws IOException {...}
}


/**
 * A GraphBuilder provides APIs to build Graph/Model/AlgoOperator from a DAG of stages, each of
 * which could be an Estimator, Model, Transformer or AlgoOperator.
 */
@PublicEvolving
public final class GraphBuilder {
    private int maxOutputLength = 20;

    public GraphBuilder() {}

    /**
     * Specifies the upper bound (could be loose) of the number of output tables that can be
     * returned by the Transformer::getModelData and AlgoOperator::transform methods, for any stage
     * involved in this Graph.
     *
     * <p>The default upper bound is 20.
     */
    public GraphBuilder setMaxOutputLength(int maxOutputLength) {...}

    /**
     * Creates a TableId associated with this GraphBuilder. It can be used to specify the passing of
     * tables between stages, as well as the input/output tables of the Graph/GraphModel generated
     * by this builder* When the graph runs as Estimator, the getModelData() of the given Model would be invoked.
     * Then when the GraphModel fitted by this graph runs, the getModelData() of the given Model
     * would be invoked.
     *
     * <p>When the graph runs as AlgoOperator or Model, the getModelData() of the given Model would
     * be invoked.
     *
     * <p>NOTE: the number of the returned TableIds does not represent the actual number of Tables
     * outputted by getModelData(). This number could be configured using {@link
     * #setMaxOutputTableNum(int)}. Users should make sure that this number >= the actual number of
     * Tables outputted by getModelData().
     *
     * @param model A Model instance.
     * @return A list of TableIds which represents the outputs of getModelData() of the given Model.
     */
    public TableId[] getModelDataFromModel(Model<?> model) {...}

    /**
     * Wraps nodes of the graph into an Estimator.
     *
     * <p>When the returned Estimator runs, and when the Model fitted by the returned Estimator
     * runs, the sequence of operations recorded by the {@code addAlgoOperator(...)}, {@code
     * addEstimator(...)}, {@code setModelData(...)} and {@code getModelData(...)} would be executed
     * as specified in the Java doc of the corresponding methods.
     *
     * @param inputs A list of TableIds which represents inputs to fit() of the returned Estimator
     *     as well as inputs to transform() of the Model fitted by the returned Estimator.
     * @param outputs A list of TableIds which represents outputs of transform() of the Model fitted
     *     by the returned Estimator.
     * @return An Estimator which wraps the nodes of this graph.
     */
    public Estimator<?, ?> buildEstimator(TableId[] inputs, TableId[] createTableId(outputs) {...}

    /**
     * Wraps nodes Ifof the stagegraph isinto an Estimator,.
   both its fit*
 method and the transform method* of<p>When itsthe fitted
returned Estimator runs, and when *the Model wouldfitted beby invokedthe withreturned theEstimator
 given inputs when the graph* runs.
, the sequence of operations *
recorded by the {@code  * <p>If this stage is a Model, Transformer or AlgoOperator, its transform method would beaddAlgoOperator(...)}, {@code
     * addEstimator(...)}, {@code setModelData(...)} and {@code getModelData(...)} would be executed
     * invokedas specified within the givenJava inputsdoc whenof the graphcorresponding runsmethods.
     *
     * @param <p>Returnsinputs aA list of TableIds, which represents outputsinputs of AlgoOperator::transform of the given stage.
     */
    public TableId[] getOutputs(Stage<?> stage, TableId... inputs) {...}

    /**to fit() of the returned Estimator
     * If this stage is anas Estimator,well itsas fitinputs methodto wouldtransform() beof invokedthe withModel estimatorInputs,fitted andby the returned Estimator.
     * @param outputs A list of TableIds which represents outputs of transform() methodof ofthe itsModel fitted Model would be invoked with modelInputs
     *     by the returned Estimator.
     *
 @param inputModelData A list *of <p>ThisTableIds methodwhich throwsrepresents Exceptioninputs ifto thesetModelData() stage is not an Estimator.of the
     *
     *Model <p>Thisfitted methodby isthe usefulreturned whenEstimator.
 the state is an Estimator* AND@param the Estimator::fit needs to take
     * a different list of Tables from the Model::transform of the fitted Model.
     *outputModelData A list of TableIds which represents outputs of getModelData() of the
     *     Model fitted by the returned Estimator.
     * <p>Returns@return aAn listEstimator of TableIds, which representswraps outputs of Model::transformthe nodes of thethis fitted Modelgraph.
     */
    public TableId[] getOutputs(Stage<?> stage, TableId[] estimatorInputs, TableId[] modelInputs) {...}

Estimator<?, ?> buildEstimator(
        /**
     * The setModelData() of the fitted GraphModel should invoke the setModelData() of the given
TableId[] inputs,
            TableId[] outputs,
       *  stage with the given inputs.TableId[] inputModelData,
     */
    public void setModelData(Stage<?> stage, TableId... inputs[] outputModelData) {...}

    /**
     * The getModelData() of the fitted GraphModel should invoke the getModelData()*
     * Wraps nodes of the given
graph into an   * stageEstimator.
     *
     * <p>Returns<p>When athe listreturned ofEstimator TableIdsruns, whichand representswhen the outputsModel offitted getModelData()by ofthe thereturned givenEstimator
     * stage.
     */ runs, the sequence of operations recorded by the {@code addAlgoOperator(...)}, {@code
    public TableId[]* getModelData(Stage<?> stage) {addEstimator(...)}, {@code setModelData(...)} and {@code getModelData(...)}

 would be  /**executed
     * as specified Returnsin anthe EstimatorJava instancedoc withof the followingcorresponding behavior:methods.
     *
     * <p>1) Estimator::fit should take the given inputs and return a Model with the following@param estimatorInputs A list of TableIds which represents inputs to fit() of the returned
     *     Estimator.
     * behavior.
@param modelInputs A list of *
TableIds which represents inputs to transform() *of <p>2)the Model::transform
 should take the given inputs* and return the given outputs.
fitted by the returned  *Estimator.
     * <p>The@param outputs fitA methodlist of theTableIds returnedwhich Estimatorrepresents andoutputs theof transform() method of the Model fitted Model
     *    should invokeby the corresponding methods of the internal stages as specified by the
     * GraphBuilder.returned Estimator.
     * @param inputModelData A list of TableIds which represents inputs to setModelData() of the
     */
    public Estimator<?, ?> buildEstimator(TableId[] inputs, TableId[] outputs) {...}

Model fitted by the returned Estimator.
     /**
 @param outputModelData A list *of ReturnsTableIds anwhich Estimatorrepresents instanceoutputs withof thegetModelData() followingof behavior:the
     *
     *Model <p>1) Estimator::fit should take the given inputs and returns a Model with the following
     * behaviorfitted by the returned Estimator.
     * @return An Estimator which wraps the nodes of this graph.
     */
     * <p>2) Model::transform should take the given inputs and return the given outputs.public Estimator<?, ?> buildEstimator(
            TableId[] estimatorInputs,
     *
     * <p>3) Model::setModelData should take the given inputModelData.
 TableId[] modelInputs,
         *
   TableId[] outputs,
 * <p>4) Model::getModelData should return the given outputModelData.
    TableId[] *inputModelData,
     *    <p>The fit method of the returned Estimator and the transform/setModelData/getModelDataTableId[] outputModelData) {...}

    /**
     * methodsWraps nodes of the fittedgraph Modelinto shouldan invokeAlgoOperator.
 the corresponding methods of the internal stages as *
     * specified by<p>When the GraphBuilder.
returned AlgoOperator runs, the sequence */
of operations recorded by public Estimator<?, ?> buildEstimator(TableId[] inputs, TableId[] outputs, TableId[] inputModelData, TableId[] outputModelData) {...}

    /**the {@code
     * addAlgoOperator(...)} and {@code addEstimator(...)} would be executed as specified in the
     * ReturnsJava andoc Estimator instanceof with the followingcorresponding behavior:methods.
     *
     * <p>1) Estimator::fit should take the given estimatorInputs and returns a Model with the @param inputs A list of TableIds which represents inputs to transform() of the returned
     *     AlgoOperator.
     * following@param behavior.
outputs A list of TableIds *
which represents outputs of transform() *of <p>2) Model::transform should take the given transformerInputs and return the given outputsthe returned
     *     AlgoOperator.
     *
 @return An AlgoOperator which *wraps <p>3) Model::setModelData should take the given inputModelDatathe nodes of this graph.
     */
     * <p>4) Model::getModelData should return the given outputModelData.
public AlgoOperator<?> buildAlgoOperator(TableId[] inputs, TableId[] outputs) {...}

     /**
     * <p>TheWraps fitnodes method of the returned Estimator and the transform/setModelData/getModelData graph into a Model.
     *
     * methods<p>When of the fittedreturned Model shouldruns, invoke the correspondingsequence methodsof ofoperations therecorded internalby stagesthe as{@code
     * specified by the GraphBuilder.
     */
    public Estimator<?, ?> buildEstimator(TableId[] estimatorInputs, TableId[] modelInputs, TableId[] outputs, TableId[] inputModelData, TableId[] outputModelData) {...}

    /*addAlgoOperator(...)} and {@code addEstimator(...)} would be executed as specified in the
     * Java doc of the corresponding methods.
     *
     * Returns@param aninputs AlgoOperatorA instancelist withof theTableIds followingwhich behavior:
represents inputs to transform() of the *returned
     * <p>1) AlgoOperator::transform should take theModel.
 given inputs and returns the* given@param outputs.
 A list of TableIds *
which represents outputs of transform() *of <p>Thethe transformreturned
 method of the returned AlgoOperator* should invoke the corresponding methodsModel.
     ** @return ofA theModel internalwhich stageswraps asthe specifiednodes byof thethis GraphBuildergraph.
     */
    public AlgoOperator<Model<?> buildAlgoOperatorbuildModel(TableId[] inputs, TableId[] outputs) {...}

    /**
     * ReturnsWraps anodes Modelof instancethe withgraph theinto followinga behavior:Model.
     *
     * <p>1) Model::transform should take <p>When the givenreturned inputsModel andruns, returns the givensequence outputs.
of operations recorded by the *{@code
     * <p>The transform method of the returned Model should invoke the corresponding methods of the* addAlgoOperator(...)}, {@code addEstimator(...)}, {@code setModelData(...)} and {@code
     * internal stages getModelData(...)} would be executed as specified byin the GraphBuilder.
Java doc of the  */corresponding
    public Model<?> buildModel(TableId[] inputs, TableId[] outputs) {...}

 * methods.
     /**
     * Returns a Model instance with the following behavior: @param inputs A list of TableIds which represents inputs to transform() of the returned
     *     Model.
     * <p>1) Model::transform should take the given inputs and returns the given outputs. @param outputs A list of TableIds which represents outputs of transform() of the returned
     *     Model.
     * <p>2) Model::setModelData should take the given inputModelData.
     *@param inputModelData A list of TableIds which represents inputs to setModelData() of the
     * <p>3) Model::getModelData should return the givenreturned outputModelDataModel.
     *
 @param outputModelData A list of TableIds * <p>The transform/setModelData/getModelData methods of the returned Model should invoke thewhich represents outputs of getModelData() of the
     *     returned Model.
     * corresponding@return methodsA ofModel thewhich internalwraps stagesthe asnodes specifiedof bythis the GraphBuildergraph.
     */
    public Model<?> buildModel(TableId[] inputs, TableId[] outputs, TableId[] inputModelData, TableId[] outputModelData) {...}
}

public class GraphNode {
    public final Stage<?> stage;
    public final TableId[] estimatorInputs;inputs,
    public final TableId[] modelInputs;
    public final TableId[] outputs;
},

public class TableId {
    private final int tableId;

    @Override
    public boolean equals(Object obj) {...}

TableId[] inputModelData,
       @Override
    public int hashCode(TableId[] outputModelData) {...}
}