FunctionMessageChunk Class — langchain Architecture

Source Code

libs/core/langchain_core/messages/function.py lines 34–62

class FunctionMessageChunk(FunctionMessage, BaseMessageChunk):
    """Function Message chunk."""

    # Ignoring mypy re-assignment here since we're overriding the value
    # to make sure that the chunk variant can be discriminated from the
    # non-chunk variant.
    type: Literal["FunctionMessageChunk"] = "FunctionMessageChunk"  # type: ignore[assignment]
    """The type of the message (used for serialization)."""

    @override
    def __add__(self, other: Any) -> BaseMessageChunk:  # type: ignore[override]
        if isinstance(other, FunctionMessageChunk):
            if self.name != other.name:
                msg = "Cannot concatenate FunctionMessageChunks with different names."
                raise ValueError(msg)

            return self.__class__(
                name=self.name,
                content=merge_content(self.content, other.content),
                additional_kwargs=merge_dicts(
                    self.additional_kwargs, other.additional_kwargs
                ),
                response_metadata=merge_dicts(
                    self.response_metadata, other.response_metadata
                ),
                id=self.id,
            )

        return super().__add__(other)