def METHOD_NAME(self, sender, receivers=None):
    """Unmute a player, so other players can hear him again.
    If <receivers> is None, the sender will be unmuted for all players
    currently on the server and all future players.
    If you want to unmute the sender only for specific players, pass a
    tuple that contains the player indexes that should hear the sender
    again.
    """
    for receiver in self._get_receivers(receivers):
        self[receiver].discard(sender)