langchain/chains/router/base.py/MultiRouteChain/_acall
class MultiRouteChain:    async def _acall(
        self,
        inputs: Dict[str, Any],
        run_manager: Optional[AsyncCallbackManagerForChainRun] = None,
    ) -> Dict[str, Any]:
        _run_manager = run_manager or CallbackManagerForChainRun.get_noop_manager()
        callbacks = _run_manager.get_child()
        route = await self.router_chain.aroute(inputs, callbacks=callbacks)

        _run_manager.on_text(
            str(route.destination) + ": " + str(route.next_inputs), verbose=self.verbose
        )
        if not route.destination:
            return await self.default_chain.acall(
                route.next_inputs, callbacks=callbacks
            )
        elif route.destination in self.destination_chains:
            return await self.destination_chains[route.destination].acall(
                route.next_inputs, callbacks=callbacks
            )
        elif self.silent_errors:
            return await self.default_chain.acall(
                route.next_inputs, callbacks=callbacks
            )
        else:
            raise ValueError(
                f"Received invalid destination chain name '{route.destination}'"
            )