Question: when does dr. hahn leave grey's anatomy
[{'answer': 'November 2008', 'provenance': [{'wikipedia_id': '13919116', 'title': 'Erica Hahn', 'start_paragraph_id': 2, 'start_character': 709, 'end_paragraph_id': 2, 'end_character': 722, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '13919116', 'title': 'Erica Hahn', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 841, 'bleu_score': 0.9844346099707091, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7362075552165469055}, 'section': 'Section::::Abstract.'}]}]