code: def add_skip_connection(self, u, v, connection_type):
          
          if connection_type not in [self.CONCAT_CONNECT, self.ADD_CONNECT]:
              raise ValueError(
                  "connection_type should be NetworkDescriptor.CONCAT_CONNECT "
                  "or NetworkDescriptor.ADD_CONNECT."
              )
          self.skip_connections.append((u, v, connection_type))
docs: Add a skip-connection to the descriptor.
          Args:
              u: Number of convolutional layers before the starting point.
              v: Number of convolutional layers before the ending point.
              connection_type: Must be either CONCAT_CONNECT or ADD_CONNECT.