code: def get_request_handler_chain(self, handler_input):
          # type: (Input) -> Union[GenericRequestHandlerChain, None]
          
          for chain in self.request_handler_chains:
              handler = chain.request_handler  # type: AbstractRequestHandler
              if handler.can_handle(handler_input=handler_input):
                  return chain
          return None
docs: Get the request handler chain that can handle the dispatch
          input.
  
          :param handler_input: Generic input passed to the
              dispatcher.
          :type handler_input: Input
          :return: Handler Chain that can handle the input.
          :rtype: Union[None, GenericRequestHandlerChain]