Question: who did the singing in the movie mamma mia
[{'answer': 'the main cast', 'provenance': [{'wikipedia_id': '8425661', 'title': 'Mamma Mia! (film)', 'start_paragraph_id': 2, 'start_character': 950, 'end_paragraph_id': 2, 'end_character': 963, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '8425661', 'title': 'Mamma Mia! (film)', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 973, 'bleu_score': 0.95865069576285, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10230536514460318442}, 'section': 'Section::::Abstract.'}]}]