Question: who wrote shake it off by taylor swift
[{'answer': 'Max Martin', 'provenance': [{'wikipedia_id': '43597651', 'title': 'Shake It Off', 'start_paragraph_id': 1, 'start_character': 157, 'end_paragraph_id': 1, 'end_character': 167, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Shellback', 'provenance': [{'wikipedia_id': '43597651', 'title': 'Shake It Off', 'start_paragraph_id': 1, 'start_character': 172, 'end_paragraph_id': 1, 'end_character': 181, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Taylor Swift', 'provenance': [{'wikipedia_id': '43597651', 'title': 'Shake It Off', 'start_paragraph_id': 1, 'start_character': 64, 'end_paragraph_id': 1, 'end_character': 76, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]