Question: who sang the songs in the movie burlesque
[{'answer': 'Christina Aguilera', 'provenance': [{'wikipedia_id': '29022460', 'title': 'Burlesque: Original Motion Picture Soundtrack', 'start_paragraph_id': 1, 'start_character': 119, 'end_paragraph_id': 1, 'end_character': 137, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Cher', 'provenance': [{'wikipedia_id': '29022460', 'title': 'Burlesque: Original Motion Picture Soundtrack', 'start_paragraph_id': 1, 'start_character': 142, 'end_paragraph_id': 1, 'end_character': 146, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '29022460', 'title': 'Burlesque: Original Motion Picture Soundtrack', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 213, 'bleu_score': 0.943604326170661, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2263843914439349423}, 'section': 'Section::::Abstract.'}]}]