Question: how many series of sons of anarchy is there
[{'answer': '7', 'provenance': [{'wikipedia_id': '18369401', 'title': 'Sons of Anarchy', 'start_paragraph_id': 20, 'start_character': 18, 'end_paragraph_id': 20, 'end_character': 19, 'bleu_score': 1.0, 'section': 'Section::::Series overview.:Season 6 (2013).\n'}]}]