)
                if filtered:
                    yield filtered
            # yield map output
            yield cast(Dict[str, Any], first_map_chunk_future.result())
            for chunk in map_output:
                yield chunk
[docs]    async def atransform(
        self,
        input: AsyncIterator[Dict[str, Any]],
        config: Optional[RunnableConfig] = None,
        **kwargs: Any,
    ) -> AsyncIterator[Dict[str, Any]]:
        # collect mapper keys
        mapper_keys = set(self.mapper.steps.keys())
        # create two streams, one for the map and one for the passthrough
        for_passthrough, for_map = atee(input, 2, lock=asyncio.Lock())
        # create map output stream
        map_output = self.mapper.atransform(for_map, config, **kwargs)
        # start map output stream
        first_map_chunk_task: asyncio.Task = asyncio.create_task(
            py_anext(map_output),  # type: ignore[arg-type]
        )
        # consume passthrough stream
        async for chunk in for_passthrough:
            assert isinstance(chunk, dict)
            # remove mapper keys from passthrough chunk, to be overwritten by map output
            filtered = AddableDict(
                {k: v for k, v in chunk.items() if k not in mapper_keys}
            )
            if filtered:
                yield filtered
        # yield map output
        yield await first_map_chunk_task
        async for chunk in map_output:
            yield chunk
[docs]    def stream(
        self,
        input: Dict[str, Any],
        config: Optional[RunnableConfig] = None,
        **kwargs: Any,
    ) -> Iterator[Dict[str, Any]]: