Question: how many nba championships have the houston rockets won
[{'answer': '2', 'provenance': [{'wikipedia_id': '72885', 'title': 'Houston Rockets', 'start_paragraph_id': 2, 'start_character': 680, 'end_paragraph_id': 2, 'end_character': 681, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]