Question: when is american ninja warrior filmed in las vegas
[{'answer': 'the national finals', 'provenance': [{'wikipedia_id': '23788991', 'title': 'American Ninja Warrior', 'start_paragraph_id': 1, 'start_character': 347, 'end_paragraph_id': 1, 'end_character': 366, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]