def test_name(self):
        """
        The name of the L{FlagConstant} instance which results from C{^}
        includes the names of only the flags which were set in exactly one of
        the two original constants.
        """
        readWrite = (self.FXF.READ | self.FXF.WRITE)
        writeAppend = (self.FXF.WRITE | self.FXF.APPEND)
        flag = readWrite ^ writeAppend
        self.assertEqual("{APPEND,READ}", flag.name)

        The name of the L{FlagConstant} instance which results from C{^}
        includes the names of only the flags which were set in exactly one of
        the two original constants.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/test/test_constants.py