Question: why is it called the mexican train game
[{'answer': 'from a special optional train', 'provenance': [{'wikipedia_id': '7727938', 'title': 'Mexican Train', 'start_paragraph_id': 1, 'start_character': 254, 'end_paragraph_id': 1, 'end_character': 283, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '7727938', 'title': 'Mexican Train', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 482, 'bleu_score': 0.9592693508045681, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12194930951168144113}, 'section': 'Section::::Abstract.'}]}]