Question: when does season 15 grey's anatomy premiere
[{'answer': 'September 27 , 2018', 'provenance': [{'wikipedia_id': '57187497', 'title': "Grey's Anatomy (season 15)", 'start_paragraph_id': 1, 'start_character': 174, 'end_paragraph_id': 1, 'end_character': 197, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '57187497', 'title': "Grey's Anatomy (season 15)", 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 461, 'bleu_score': 0.7838717269994661, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7721235291013516433}, 'section': 'Section::::Abstract.'}]}]