code: def tick(self):
      
  
      # Run activities whose time has come
      for act in self.__activities:
        if not act.iteratorHolder[0]:
          continue
  
        try:
          next(act.iteratorHolder[0])
        except StopIteration:
          act.cb()
          if act.repeating:
            act.iteratorHolder[0] = iter(xrange(act.period))
          else:
            act.iteratorHolder[0] = None
  
      return True
docs: Activity tick handler; services all activities
  
      Returns:      True if controlling iterator says it's okay to keep going;
                    False to stop