Question: who wrote the song let's stay together
[{'answer': 'Al Green', 'provenance': [{'wikipedia_id': '1215326', 'title': "Let's Stay Together", 'start_paragraph_id': 3, 'start_character': 35, 'end_paragraph_id': 3, 'end_character': 43, 'bleu_score': 1.0, 'section': 'Section::::Music.\n'}]}, {'answer': 'Willie Mitchell'}, {'answer': 'Al Jackson , Jr .'}]