Question: who sang lead on i am the walrus
[{'answer': 'John Lennon', 'provenance': [{'wikipedia_id': '143172', 'title': 'I Am the Walrus', 'start_paragraph_id': 42, 'start_character': 12, 'end_paragraph_id': 42, 'end_character': 23, 'bleu_score': 1.0, 'section': 'Section::::Personnel.\n'}]}]