docs: def callLater(self, when, what, *a, **kw):
      """
      Copied from twisted.internet.task.Clock, r20480.  Fixes the bug
      where the wrong DelayedCall would sometimes be returned.
      """
      dc =  base.DelayedCall(self.seconds() + when,
                             what, a, kw,
                             self.calls.remove,
                             lambda c: None,
                             self.seconds)
      self.calls.append(dc)
      self.calls.sort(lambda a, b: cmp(a.getTime(), b.getTime()))
      return dc