Question: when does preston burke come back to grey's anatomy
[{'answer': 'tenth season', 'provenance': [{'wikipedia_id': '9019239', 'title': 'Preston Burke', 'start_paragraph_id': 3, 'start_character': 85, 'end_paragraph_id': 3, 'end_character': 97, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '9019239', 'title': 'Preston Burke', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 160, 'bleu_score': 0.9214109120166031, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8885410556106230097}, 'section': 'Section::::Abstract.'}]}]