Question: who led an all black american cavalry unit
[{'answer': 'Benjamin Grierson', 'provenance': [{'wikipedia_id': '303103', 'title': 'Buffalo Soldier', 'start_paragraph_id': 9, 'start_character': 300, 'end_paragraph_id': 9, 'end_character': 317, 'bleu_score': 1.0, 'section': 'Section::::Etymology.\n'}]}, {'answer': 'Edward Hatch', 'provenance': [{'wikipedia_id': '303103', 'title': 'Buffalo Soldier', 'start_paragraph_id': 12, 'start_character': 317, 'end_paragraph_id': 12, 'end_character': 329, 'bleu_score': 1.0, 'section': 'Section::::Service.\n'}]}, {'answer': 'Louis H. Carpenter', 'provenance': [{'wikipedia_id': '303103', 'title': 'Buffalo Soldier', 'start_paragraph_id': 12, 'start_character': 356, 'end_paragraph_id': 12, 'end_character': 374, 'bleu_score': 1.0, 'section': 'Section::::Service.\n'}]}, {'answer': 'Nicholas M. Nolan', 'provenance': [{'wikipedia_id': '303103', 'title': 'Buffalo Soldier', 'start_paragraph_id': 12, 'start_character': 376, 'end_paragraph_id': 12, 'end_character': 393, 'bleu_score': 1.0, 'section': 'Section::::Service.\n'}]}, {'answer': 'Henry O. Flipper', 'provenance': [{'wikipedia_id': '303103', 'title': 'Buffalo Soldier', 'start_paragraph_id': 12, 'start_character': 509, 'end_paragraph_id': 12, 'end_character': 525, 'bleu_score': 1.0, 'section': 'Section::::Service.\n'}]}]