<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def execute_route(self, meta_data, request_pdu):
 """ Execute configured route based on requests meta data and request PDU. :param meta_data: A dict with meta data. It must at least contain key 'unit_id'. :param request_pdu: A bytearray containing request PDU. :return: A bytearry containing reponse PDU. """

        try:
            function = create_function_from_request_pdu(request_pdu)
            results =\
                function.execute(meta_data['unit_id'], self.route_map)

            try:
                # ReadFunction's use results of callbacks to build response
                # PDU...
                return function.create_response_pdu(results)
            except TypeError:
                # ...other functions don't.
                return function.create_response_pdu()
        except ModbusError as e:
            function_code = get_function_code_from_request_pdu(request_pdu)
            return pack_exception_pdu(function_code, e.error_code)
        except Exception as e:
            log.exception('Could not handle request: {0}.'.format(e))
            function_code = get_function_code_from_request_pdu(request_pdu)

            return pack_exception_pdu(function_code,
                                      ServerDeviceFailureError.error_code)