Question: when was the first gastric bypass surgery performed
[{'answer': '1997', 'provenance': [{'wikipedia_id': '781984', 'title': 'Gastric bypass surgery', 'start_paragraph_id': 30, 'start_character': 88, 'end_paragraph_id': 30, 'end_character': 92, 'bleu_score': 1.0, 'section': 'Section::::Surgical techniques.:Variations.:"Mini-gastric bypass" (MGB).\n'}]}, {'provenance': [{'wikipedia_id': '781984', 'title': 'Gastric bypass surgery', 'start_paragraph_id': 30, 'start_character': 0, 'end_paragraph_id': 30, 'end_character': 371, 'bleu_score': 0.970795021215021, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 804641542821358087}, 'section': 'Section::::Surgical techniques.:Variations.:"Mini-gastric bypass" (MGB).\n'}]}]