Question: who plays derek's wife in grey's anatomy
[{'answer': 'Kate Walsh', 'provenance': [{'wikipedia_id': '7687031', 'title': 'Addison Montgomery', 'start_paragraph_id': 1, 'start_character': 174, 'end_paragraph_id': 1, 'end_character': 184, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]