Question: who sang man of constant sorrow for o brother where art thou
[{'answer': 'Dan Tyminski', 'provenance': [{'wikipedia_id': '3867521', 'title': 'Man of Constant Sorrow', 'start_paragraph_id': 3, 'start_character': 177, 'end_paragraph_id': 3, 'end_character': 189, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '3867521', 'title': 'Man of Constant Sorrow', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 379, 'bleu_score': 0.9699161750394991, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15403136576965712178}, 'section': 'Section::::Abstract.'}]}]