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/**
 * Interface for classes that take parameters. It provides APIs to set and get parameters.
 *
 * @param <T> The class type of WithParams implementation itself.
 */
@PublicEvolving
public interface WithParams<T> {
    /** Gets a param by name. */
    default <V> Param<V> getParam(String name) {...}

    /**
     * Sets the value of the given parameter in the user-defined map.
     *
     * @param param the parameter
     * @param value the value
     * @return the WithParams instance itself
     */
    default <V> T set(Param<V> param, V value) {...}

    /**
     * Gets the value of the given parameter. Returns the value from the user-defined map if set(...) has been
     * explicitly called to set value for this parameter. Otherwise, returns the default value from the definition of
     * this parameter.
     *
     * @param param the parameter
     * @param <V> the type of the parameter
     * @return the value of the parameter
     */
    default <V> V get(Param<V> param) {...}

    /**
     * Returns an immutable map that contains value for every parameter that meets one of the following conditions:
     * 1) set(...) has been called to set value for this parameter.
     * 2) The parameter is a public field of this WithParams instance. This includes public, protected and private fields. And
     * this also includes fields inherited from its interfaces and super-classes.     
     *
     * @return an immutable map of parameters and values.
     */
    default Map<Param<?>, Object> getParamMap() {...}

    /**
     * A subclass of this interface should override this method to provide a mutable map that can be used to store 
     * parameter values.
     *
     * @return a mutable map from param to param value.
     */
    Map<Param<?>, Object> getUserDefinedParamMap();
}