def tick(self):
<EOL>for act in self.__activities:<EOL><INDENT>if not act.iteratorHolder[<NUM_LIT:0>]:<EOL><INDENT>continue<EOL><DEDENT>try:<EOL><INDENT>next(act.iteratorHolder[<NUM_LIT:0>])<EOL><DEDENT>except StopIteration:<EOL><INDENT>act.cb()<EOL>if act.repeating:<EOL><INDENT>act.iteratorHolder[<NUM_LIT:0>] = iter(range(act.period-<NUM_LIT:1>))<EOL><DEDENT>else:<EOL><INDENT>act.iteratorHolder[<NUM_LIT:0>] = None<EOL><DEDENT><DEDENT><DEDENT>return True<EOL>
Activity tick handler; services all activities

        Returns:
          True if controlling iterator says it's okay to keep going;
          False to stop