Question: how many books are in the sherlock holmes series
[{'answer': 'four', 'provenance': [{'wikipedia_id': '27159', 'title': 'Sherlock Holmes', 'start_paragraph_id': 2, 'start_character': 283, 'end_paragraph_id': 2, 'end_character': 287, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '27159', 'title': 'Sherlock Holmes', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 651, 'bleu_score': 0.9815648442794911, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8554156199923161581}, 'section': 'Section::::Abstract.'}]}]