Question: who sings backup on in the blood john mayer
[{'answer': 'Sheryl Crow', 'provenance': [{'wikipedia_id': '52314606', 'title': 'The Search for Everything', 'start_paragraph_id': 21, 'start_character': 12, 'end_paragraph_id': 21, 'end_character': 23, 'bleu_score': 1.0, 'section': 'Section::::Personnel.:Musicians.\n'}]}]