Question: when did the fitbit charge 2 come out
[{'answer': '2017', 'provenance': [{'wikipedia_id': '52308828', 'title': 'List of Fitbit products', 'start_paragraph_id': 8, 'start_character': 12, 'end_paragraph_id': 8, 'end_character': 16, 'bleu_score': 1.0, 'section': 'Section::::Current products.:Wristband trackers.:Fitbit Flex 2.\n'}]}]