<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def warn_once(self, msg, msg_name=None):
 """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. """

        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)