Question: when did series 4 of sherlock come out
[{'answer': '1 January 2017', 'provenance': [{'wikipedia_id': '20816992', 'title': 'Sherlock (TV series)', 'start_paragraph_id': 32, 'start_character': 689, 'end_paragraph_id': 32, 'end_character': 703, 'bleu_score': 1.0, 'section': 'Section::::Episodes.\n'}]}]