def test_representation(self):
        """
        The string representation of a L{FlagConstant} instance which results
        from C{&} includes the names of only the flags which were set in both
        both of the two original constants.
        """
        readWrite = (self.FXF.READ | self.FXF.WRITE)
        writeAppend = (self.FXF.WRITE | self.FXF.APPEND)
        flag = readWrite & writeAppend
        self.assertEqual("<FXF=WRITE>", repr(flag))

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