langchain/callbacks/aim_callback.py/AimCallbackHandler/on_chain_start
class AimCallbackHandler:    def on_chain_start(
        self, serialized: Dict[str, Any], inputs: Dict[str, Any], **kwargs: Any
    ) -> None:
        """Run when chain starts running."""
        aim = import_aim()
        self.step += 1
        self.chain_starts += 1
        self.starts += 1

        resp = {"action": "on_chain_start"}
        resp.update(self.get_custom_callback_meta())

        inputs_res = deepcopy(inputs)

        self._run.track(
            aim.Text(inputs_res["input"]), name="on_chain_start", context=resp
        )