Question: when did alcatraz open as a federal prison
[{'answer': '1934', 'provenance': [{'wikipedia_id': '64107', 'title': 'Alcatraz Island', 'start_paragraph_id': 1, 'start_character': 244, 'end_paragraph_id': 1, 'end_character': 248, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '64107', 'title': 'Alcatraz Island', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 630, 'bleu_score': 0.828766654473684, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4243545677781939502}, 'section': 'Section::::Abstract.'}]}]