Question: whens the last time there was a sweep in the nba finals
[{'answer': '2018', 'provenance': [{'wikipedia_id': '4516513', 'title': '2007 NBA Finals', 'start_paragraph_id': 2, 'start_character': 55, 'end_paragraph_id': 2, 'end_character': 59, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]