Question: american singer who sang i left my heart in san francisco
[{'answer': 'Tony Bennett', 'provenance': [{'wikipedia_id': '1872941', 'title': 'I Left My Heart in San Francisco', 'start_paragraph_id': 1, 'start_character': 212, 'end_paragraph_id': 1, 'end_character': 224, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]