def test_identity(self):
        """
        Test to make sure that objects retain identity properly.
        """
        x = []
        y = (x)
        x.append(y)
        x.append(y)
        self.assertIs(x[0], x[1])
        self.assertIs(x[0][0], x)
        s = jelly.jelly(x)
        z = jelly.unjelly(s)
        self.assertIs(z[0], z[1])
        self.assertIs(z[0][0], z)

        Test to make sure that objects retain identity properly.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/spread/test/test_jelly.py