dispatch_custom_event

Example:

from langchain_core.callbacks import BaseCallbackHandler
from langchain_core.callbacks import dispatch_custom_event
from langchain_core.runnable import RunnableLambda

class CustomCallbackManager(BaseCallbackHandler):
    def on_custom_event(
        self,
        name: str,
        data: Any,
        *,
        run_id: UUID,
        tags: list[str] | None = None,
        metadata: dict[str, Any] | None = None,
        **kwargs: Any,
    ) -> None:
        print(f"Received custom event: {name} with data: {data}")

def foo(inputs):
    dispatch_custom_event("my_event", {"bar": "buzz})
    return inputs

foo_ = RunnableLambda(foo)
foo_.invoke({"a": "1"}, {"callbacks": [CustomCallbackManager()]})