Question: when does season 12 of americas got talent end
[{'answer': 'September 20', 'provenance': [{'wikipedia_id': '4829129', 'title': "America's Got Talent", 'start_paragraph_id': 63, 'start_character': 60, 'end_paragraph_id': 63, 'end_character': 72, 'bleu_score': 1.0, 'section': 'Section::::Season synopses.:Season 12 (2017).\n'}]}]