Question: how many series are there of american horror story
[{'answer': '8', 'provenance': [{'wikipedia_id': '31227103', 'title': 'American Horror Story', 'start_paragraph_id': 2, 'start_character': 1544, 'end_paragraph_id': 2, 'end_character': 1545, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]