CallbackManagerMixin Class — langchain Architecture

Source Code

libs/core/langchain_core/callbacks/base.py lines 238–371

class CallbackManagerMixin:
    """Mixin for callback manager."""

    def on_llm_start(
        self,
        serialized: dict[str, Any],
        prompts: list[str],
        *,
        run_id: UUID,
        parent_run_id: UUID | None = None,
        tags: list[str] | None = None,
        metadata: dict[str, Any] | None = None,
        **kwargs: Any,
    ) -> Any:
        """Run when LLM starts running.

        !!! warning

            This method is called for non-chat models (regular text completion LLMs). If
            you're implementing a handler for a chat model, you should use
            `on_chat_model_start` instead.

        Args:
            serialized: The serialized LLM.
            prompts: The prompts.
            run_id: The ID of the current run.
            parent_run_id: The ID of the parent run.
            tags: The tags.
            metadata: The metadata.
            **kwargs: Additional keyword arguments.
        """

    def on_chat_model_start(
        self,
        serialized: dict[str, Any],
        messages: list[list[BaseMessage]],
        *,
        run_id: UUID,
        parent_run_id: UUID | None = None,
        tags: list[str] | None = None,
        metadata: dict[str, Any] | None = None,
        **kwargs: Any,
    ) -> Any:
        """Run when a chat model starts running.

        !!! warning

            This method is called for chat models. If you're implementing a handler for
            a non-chat model, you should use `on_llm_start` instead.

        Args:
            serialized: The serialized chat model.
            messages: The messages.
            run_id: The ID of the current run.
            parent_run_id: The ID of the parent run.
            tags: The tags.
            metadata: The metadata.
            **kwargs: Additional keyword arguments.
        """
        # NotImplementedError is thrown intentionally
        # Callback handler will fall back to on_llm_start if this is exception is thrown
        msg = f"{self.__class__.__name__} does not implement `on_chat_model_start`"
        raise NotImplementedError(msg)

    def on_retriever_start(
        self,
        serialized: dict[str, Any],
        query: str,
        *,
        run_id: UUID,
        parent_run_id: UUID | None = None,
        tags: list[str] | None = None,
        metadata: dict[str, Any] | None = None,
        **kwargs: Any,
    ) -> Any:
        """Run when the `Retriever` starts running.

        Args:
            serialized: The serialized `Retriever`.
            query: The query.
            run_id: The ID of the current run.