Question: who are the winning coaches of the voice
[{'answer': 'Adam Levine', 'provenance': [{'wikipedia_id': '31015127', 'title': 'The Voice (American TV series)', 'start_paragraph_id': 3, 'start_character': 323, 'end_paragraph_id': 3, 'end_character': 334, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Blake Shelton', 'provenance': [{'wikipedia_id': '31015127', 'title': 'The Voice (American TV series)', 'start_paragraph_id': 3, 'start_character': 340, 'end_paragraph_id': 3, 'end_character': 353, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Usher', 'provenance': [{'wikipedia_id': '31015127', 'title': 'The Voice (American TV series)', 'start_paragraph_id': 3, 'start_character': 518, 'end_paragraph_id': 3, 'end_character': 523, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Pharrell Williams', 'provenance': [{'wikipedia_id': '31015127', 'title': 'The Voice (American TV series)', 'start_paragraph_id': 3, 'start_character': 525, 'end_paragraph_id': 3, 'end_character': 542, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Christina Aguilera', 'provenance': [{'wikipedia_id': '31015127', 'title': 'The Voice (American TV series)', 'start_paragraph_id': 3, 'start_character': 290, 'end_paragraph_id': 3, 'end_character': 308, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Alicia Keys', 'provenance': [{'wikipedia_id': '31015127', 'title': 'The Voice (American TV series)', 'start_paragraph_id': 3, 'start_character': 557, 'end_paragraph_id': 3, 'end_character': 568, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]