Question: who sings the song leaving on a jet plane
[{'answer': 'John Denver', 'provenance': [{'wikipedia_id': '5323589', 'title': 'Leaving on a Jet Plane', 'start_paragraph_id': 1, 'start_character': 46, 'end_paragraph_id': 1, 'end_character': 57, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Peter , Paul and Mary', 'provenance': [{'wikipedia_id': '5323589', 'title': 'Leaving on a Jet Plane', 'start_paragraph_id': 2, 'start_character': 20, 'end_paragraph_id': 2, 'end_character': 42, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '5323589', 'title': 'Leaving on a Jet Plane', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 412, 'bleu_score': 0.9748377259086851, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 14595059963023600873}, 'section': 'Section::::Abstract.'}]}]