Question: when was the song imagine written by john lennon
[{'answer': '1971', 'provenance': [{'wikipedia_id': '18960141', 'title': 'Imagine (John Lennon song)', 'start_paragraph_id': 2, 'start_character': 159, 'end_paragraph_id': 2, 'end_character': 163, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '18960141', 'title': 'Imagine (John Lennon song)', 'start_paragraph_id': 8, 'start_character': 0, 'end_paragraph_id': 8, 'end_character': 960, 'bleu_score': 0.831082322322466, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10702523798495131559}, 'section': 'Section::::Composition and writing.\n'}]}]