Question: who sings the song man of constant sorrow
[{'answer': 'Emry Arthur', 'provenance': [{'wikipedia_id': '3867521', 'title': 'Man of Constant Sorrow', 'start_paragraph_id': 1, 'start_character': 310, 'end_paragraph_id': 1, 'end_character': 321, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '3867521', 'title': 'Man of Constant Sorrow', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 369, 'bleu_score': 0.968982777549629, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6798321585565815099}, 'section': 'Section::::Abstract.'}]}]