Question: who was the creator of keystone film corp and specialized in slapstick comedy films
[{'answer': 'Mack Sennett', 'provenance': [{'wikipedia_id': '730625', 'title': 'Keystone Studios', 'start_paragraph_id': 1, 'start_character': 160, 'end_paragraph_id': 1, 'end_character': 172, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '730625', 'title': 'Keystone Studios', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 734, 'bleu_score': 0.9410451604405151, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 18075873848932830943}, 'section': 'Section::::Production.\n'}]}]