Question: who wrote the ballad of pancho and lefty
[{'answer': 'Townes Van Zandt', 'provenance': [{'wikipedia_id': '773571', 'title': 'Pancho and Lefty', 'start_paragraph_id': 1, 'start_character': 61, 'end_paragraph_id': 1, 'end_character': 77, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '773571', 'title': 'Pancho and Lefty', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 216, 'bleu_score': 0.948006874591591, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12349007704598097640}, 'section': 'Section::::Abstract.'}]}]