def pump(self):
        """
        Do all of the work that is currently available to be done.
        """
        work, self.work = self.work, []
        for unit in work:
            if not unit.cancelled:
                unit.func()

        Do all of the work that is currently available to be done.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_cooperator.py