RunnableBindingBase Class — langchain Architecture

Source Code

libs/core/langchain_core/runnables/base.py lines 5530–5929

class RunnableBindingBase(RunnableSerializable[Input, Output]):  # type: ignore[no-redef]
    """`Runnable` that delegates calls to another `Runnable` with a set of `**kwargs`.

    Use only if creating a new `RunnableBinding` subclass with different `__init__`
    args.

    See documentation for `RunnableBinding` for more details.

    """

    bound: Runnable[Input, Output]
    """The underlying `Runnable` that this `Runnable` delegates to."""

    kwargs: Mapping[str, Any] = Field(default_factory=dict)
    """kwargs to pass to the underlying `Runnable` when running.

    For example, when the `Runnable` binding is invoked the underlying
    `Runnable` will be invoked with the same input but with these additional
    kwargs.

    """

    config: RunnableConfig = Field(default_factory=RunnableConfig)
    """The config to bind to the underlying `Runnable`."""

    config_factories: list[Callable[[RunnableConfig], RunnableConfig]] = Field(
        default_factory=list
    )
    """The config factories to bind to the underlying `Runnable`."""

    # Union[Type[Input], BaseModel] + things like list[str]
    custom_input_type: Any | None = None
    """Override the input type of the underlying `Runnable` with a custom type.

    The type can be a Pydantic model, or a type annotation (e.g., `list[str]`).
    """
    # Union[Type[Output], BaseModel] + things like list[str]
    custom_output_type: Any | None = None
    """Override the output type of the underlying `Runnable` with a custom type.

    The type can be a Pydantic model, or a type annotation (e.g., `list[str]`).
    """

    model_config = ConfigDict(
        arbitrary_types_allowed=True,
    )

    def __init__(
        self,
        *,
        bound: Runnable[Input, Output],
        kwargs: Mapping[str, Any] | None = None,
        config: RunnableConfig | None = None,
        config_factories: list[Callable[[RunnableConfig], RunnableConfig]]
        | None = None,
        custom_input_type: type[Input] | BaseModel | None = None,
        custom_output_type: type[Output] | BaseModel | None = None,
        **other_kwargs: Any,
    ) -> None:
        """Create a `RunnableBinding` from a `Runnable` and kwargs.

        Args:
            bound: The underlying `Runnable` that this `Runnable` delegates calls
                to.
            kwargs: optional kwargs to pass to the underlying `Runnable`, when running
                the underlying `Runnable` (e.g., via `invoke`, `batch`,
                `transform`, or `stream` or async variants)

            config: optional config to bind to the underlying `Runnable`.

            config_factories: optional list of config factories to apply to the
                config before binding to the underlying `Runnable`.

            custom_input_type: Specify to override the input type of the underlying
                `Runnable` with a custom type.
            custom_output_type: Specify to override the output type of the underlying
                `Runnable` with a custom type.
            **other_kwargs: Unpacked into the base class.
        """
        super().__init__(
            bound=bound,