code: def _generate_route_method_decl(
              self, namespace, route, arg_data_type, request_binary_body,
              method_name_suffix='', extra_args=None):
          
          args = ['self']
          if extra_args:
              args += extra_args
          if request_binary_body:
              args.append('f')
          if is_struct_type(arg_data_type):
              for field in arg_data_type.all_fields:
                  if is_nullable_type(field.data_type):
                      args.append('{}=None'.format(field.name))
                  elif field.has_default:
                      # TODO(kelkabany): Decide whether we really want to set the
                      # default in the argument list. This will send the default
                      # over the wire even if it isn't overridden. The benefit is
                      # it locks in a default even if it is changed server-side.
                      if is_user_defined_type(field.data_type):
                          ns = field.data_type.namespace
                      else:
                          ns = None
                      arg = '{}={}'.format(
                          field.name,
                          self._generate_python_value(ns, field.default))
                      args.append(arg)
                  else:
                      args.append(field.name)
          elif is_union_type(arg_data_type):
              args.append('arg')
          elif not is_void_type(arg_data_type):
              raise AssertionError('Unhandled request type: %r' %
                                   arg_data_type)
  
          method_name = fmt_func(route.name + method_name_suffix, version=route.version)
          namespace_name = fmt_underscores(namespace.name)
          self.generate_multiline_list(args, 'def {}_{}'.format(namespace_name, method_name), ':')
docs: Generates the method prototype for a route.