Question: who holds the record for the fastest tennis serve
[{'answer': 'John Isner', 'provenance': [{'wikipedia_id': '23482103', 'title': 'Fastest recorded tennis serves', 'start_paragraph_id': 4, 'start_character': 473, 'end_paragraph_id': 4, 'end_character': 483, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '23482103', 'title': 'Fastest recorded tennis serves', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 542, 'bleu_score': 0.6233717607017161, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 971796045222552669}, 'section': 'Section::::Abstract.'}]}]