Question: when was the union building built in pretoria
[{'answer': '1913', 'provenance': [{'wikipedia_id': '468686', 'title': 'Union Buildings', 'start_paragraph_id': 17, 'start_character': 212, 'end_paragraph_id': 17, 'end_character': 216, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}]