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The new methods on `KTableImpl` will add a new KTableTransformValues processor node and attach any state stores.  The new KTableTransformValues will be implemented in a similar manner to other processors, instantiating the user supplied transformer once per task.

The `ProcessorContext` passed to the `init()` method of transformer implementations will be restricted. Any call to any variant of the `forward()` method will throw a `StreamsException`, otherwise implementations could output values with a new key. Any call to `getStateStore` where the requested store is the one passed in via the `materialized` parameter will throw a `StreamsException`, as this state store is managed by the the streams library.

Compatibility, Deprecation, and Migration Plan

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