code: def is_legal(self, layers=None):
          '''
          Judge whether is legal for layers
          '''
          if layers is None:
              layers = self.layers
  
          for layer in layers:
              if layer.is_delete is False:
                  if len(layer.input) != layer.input_size:
                      return False
                  if len(layer.output) < layer.output_size:
                      return False
  
          # layer_num <= max_layer_num
          if self.layer_num(layers) > self.max_layer_num:
              return False
  
          # There is loop in graph || some layers can't to arrive
          if self.is_topology(layers) is False:
              return False
  
          return Truf is_legal(self, layers=None):
          '''
          Judge whether is legal for layers
          '''
          if layers is None:
              layers = self.layers
  
          for layer in layers:
              if layer.is_delete is False:
                  if len(layer.input) != layer.input_size:
                      return False
                  if len(layer.output) < layer.output_size:
                      return False
  
          # layer_num <= max_layer_num
          if self.layer_num(layers) > self.max_layer_num:
              return False
  
          # There is loop in graph || some layers can't to arrive
          if self.is_topology(layers) is False:
              return False
  
          return True
docs: Judge whether is legal for layers