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The `ProcessorContext` passed to the `init()` method of transformer implementations will be restricted. Any : any call to any variant of the `forward()` method will throw a `StreamsException`, otherwise implementations could output . This will stop implementations outputting 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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