def METHOD_NAME(self):
    source_file = io.StringIO("Subject: bogus\n\nmsg\n")
    msg = email.message_from_file(source_file,
                                  self.MyMessage,
                                  policy=self.MyPolicy)
    self.assertIsInstance(msg, self.MyMessage)
    self.assertIs(msg.check_policy, self.MyPolicy)