Question: how many the mortal instruments books are there
[{'answer': '6', 'provenance': [{'wikipedia_id': '22761800', 'title': 'The Mortal Instruments', 'start_paragraph_id': 27, 'start_character': 319, 'end_paragraph_id': 27, 'end_character': 320, 'bleu_score': 1.0, 'section': 'Section::::Critical reception.\n'}]}]