<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def unjoin(self):
 """Remove this speaker from a group. Seems to work ok even if you remove what was previously the group master from it's own group. If the speaker was not in a group also returns ok. """


        self.avTransport.BecomeCoordinatorOfStandaloneGroup([
            ('InstanceID', 0)
        ])
        self._zgs_cache.clear()
        self._parse_zone_group_state()