code: def connect(self, callback, ref=False, position='first',
                  before=None, after=None):
          
          self._connect_emitters(True)
          return EventEmitter.connect(self, callback, ref, position,
                                      before, after)
docs: Connect the callback to the event group. The callback will receive
          events from *all* of the emitters in the group.
  
          See :func:`EventEmitter.connect() <vispy.event.EventEmitter.connect>`
          for arguments.