code: def warn_once(self, msg, msg_name=None):
          
          assert isinstance(msg, str)
          msg_name = msg_name if msg_name else msg
          if msg_name not in warnings_given:
              warnings.warn(msg)
          warnings_given.add(msg_name)
docs: Prints a warning statement just once
  
          Args:
              msg: The warning message
              msg_name: [optional] The name of the warning. If None, the msg_name
                  will be the msg itself.