Question: who played gayle sayers in brian's song
[{'answer': 'Billy Dee Williams', 'provenance': [{'wikipedia_id': '2212664', 'title': "Brian's Song", 'start_paragraph_id': 1, 'start_character': 274, 'end_paragraph_id': 1, 'end_character': 292, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '2212664', 'title': "Brian's Song", 'start_paragraph_id': 11, 'start_character': 0, 'end_paragraph_id': 11, 'end_character': 45, 'bleu_score': 0.6803749333171201, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3018408354594696779}, 'section': 'Section::::Cast.\n'}]}]