Question: who discovered the different valves of the heart
[{'answer': 'Erasistratos', 'provenance': [{'wikipedia_id': '36808', 'title': 'Heart', 'start_paragraph_id': 127, 'start_character': 558, 'end_paragraph_id': 127, 'end_character': 570, 'bleu_score': 1.0, 'section': 'Section::::History.:Ancient.\n'}]}, {'provenance': [{'wikipedia_id': '36808', 'title': 'Heart', 'start_paragraph_id': 127, 'start_character': 0, 'end_paragraph_id': 127, 'end_character': 853, 'bleu_score': 0.9589968276238241, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13566094768493529020}, 'section': 'Section::::History.:Ancient.\n'}]}]