def test_repr(self):
        """
        The C{repr()} of a L{Deferred} contains the class name and a
        representation of the internal Python ID.
        """
        d = defer.Deferred()
        address = id(d)
        self.assertEqual(
            repr(d), '<Deferred at 0x%x>' % (address,))

        The C{repr()} of a L{Deferred} contains the class name and a
        representation of the internal Python ID.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_defer.py