def test_str(self):
        """
        The string representation of a L{DelayedCall} instance, as returned by
        L{str}, includes the unsigned id of the instance, as well as its state,
        the function to be called, and the function arguments.
        """
        dc = DelayedCall(12, nothing, (3, ), {"A": 5}, None, None, lambda: 1.5)
        expectedRegexp = (
            "<DelayedCall 0x{:x} \\[10.5s\\] called=0 cancelled=0 "
            "nothing\\(3, A=5\\)\n\n"
            "traceback at creation:".format(id(dc)))
        self.assertRegex(
            str(dc), expectedRegexp)

        The string representation of a L{DelayedCall} instance, as returned by
        L{str}, includes the unsigned id of the instance, as well as its state,
        the function to be called, and the function arguments.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/test/test_base.py