Question: who sang the song let it go in the movie frozen
[{'answer': 'Idina Menzel', 'provenance': [{'wikipedia_id': '41245530', 'title': 'Let It Go (Disney song)', 'start_paragraph_id': 1, 'start_character': 288, 'end_paragraph_id': 1, 'end_character': 300, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]