Question: who performed the first successful human heart operation
[{'answer': 'Christiaan Neethling Barnard', 'provenance': [{'wikipedia_id': '7015', 'title': 'Christiaan Barnard', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 28, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '7015', 'title': 'Christiaan Barnard', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 778, 'bleu_score': 0.717227958913719, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4597418906398332967}, 'section': 'Section::::Abstract.'}]}]