Question: who sings let it go at the end of the movie frozen
[{'answer': 'Demi Lovato', 'provenance': [{'wikipedia_id': '41245530', 'title': 'Let It Go (Disney song)', 'start_paragraph_id': 1, 'start_character': 484, 'end_paragraph_id': 1, 'end_character': 495, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '41245530', 'title': 'Let It Go (Disney song)', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 599, 'bleu_score': 0.9806740509884301, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 14032464668392633200}, 'section': 'Section::::Abstract.'}]}]