Question: who plays derek shepherd in grey's anatomy
[{'answer': 'Patrick Dempsey', 'provenance': [{'wikipedia_id': '711747', 'title': 'Patrick Dempsey', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 15, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '711747', 'title': 'Patrick Dempsey', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 753, 'bleu_score': 0.8795545713537891, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3384399478320402078}, 'section': 'Section::::Abstract.'}]}]