def callLater(self, _seconds, _f, *args, **kw):
        """See twisted.internet.interfaces.IReactorTime.callLater.
        """
        assert callable(_f), "%s is not callable" % _f
        assert _seconds >= 0, \
               "%s is not greater than or equal to 0 seconds" % (_seconds,)
        tple = DelayedCall(self.seconds() + _seconds, _f, args, kw,
                           self._cancelCallLater,
                           self._moveCallLaterSooner,
                           seconds=self.seconds)
        self._newTimedCalls.append(tple)
        return tple
See twisted.internet.interfaces.IReactorTime.callLater.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/base.py