Question: when did the forbidden city became a museum
[{'answer': '1925', 'provenance': [{'wikipedia_id': '12817274', 'title': 'History of the Forbidden City', 'start_paragraph_id': 2, 'start_character': 196, 'end_paragraph_id': 2, 'end_character': 200, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '12817274', 'title': 'History of the Forbidden City', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 258, 'bleu_score': 0.9560167778278961, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6193029623459664441}, 'section': 'Section::::Abstract.'}]}]