def test_namespaceInheritance(self):
        """
        Check that unspecified namespace is a thing separate from undefined
        namespace. This test added after discovering some weirdness in Lore.
        """
        # will only work if childNodes is mutated. not sure why.
        child = microdom.Element('ol')
        parent = microdom.Element('div', namespace='http://www.w3.org/1999/xhtml')
        parent.childNodes = [child]
        self.assertEqual(parent.toxml(),
                          '<div xmlns="http://www.w3.org/1999/xhtml"><ol></ol></div>')

        Check that unspecified namespace is a thing separate from undefined
        namespace. This test added after discovering some weirdness in Lore.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_xml.py