Question: who played dr. burke on grey's anatomy
[{'answer': 'Isaiah Washington IV', 'provenance': [{'wikipedia_id': '3317052', 'title': 'Isaiah Washington', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 20, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '3317052', 'title': 'Isaiah Washington', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 321, 'bleu_score': 0.5569594494250091, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2052680621481790150}, 'section': 'Section::::Abstract.'}]}]