<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def GetPossibleGroup(self):
 """Returns a possible group from the end of the call queue or None if no other methods are on the stack. """


    # Remove this method from the tail of the queue so we can add it to a group.
    this_method = self._call_queue.pop()
    assert this_method == self

    # Determine if the tail of the queue is a group, or just a regular ordered
    # mock method.
    group = None
    try:
      group = self._call_queue[-1]
    except IndexError:
      pass

    return group