def METHOD_NAME(self):
    if 'X-GP-SEQ' not in self.headers:
        self.log_message('X-GP-SEQ expected.')
        simple_exit()
    current_seq = int(self.headers['X-GP-SEQ'])
    self.log_message('incoming X-GP-SEQ:%d' % current_seq)
    if current_seq != TestSequenceHandler.expected_seq:
        self.log_message('X-GP-SEQ:%d expected, but %d found.' %
                    (TestSequenceHandler.expected_seq, current_seq))
        simple_exit()
    response_with_code(self, 200)
    TestSequenceHandler.expected_seq = current_seq + 1