<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _send_to_destinations(self, destinations, message, header=None, **kwargs):
 """Send messages to a list of numbered destinations. This is an internal helper method used by the public 'send' methods. """

        if not isinstance(destinations, list):
            destinations = (destinations,)
        for destination in destinations:
            self._send_to_destination(destination, header, message, kwargs)