Question: when did the netherlands became a constitutional monarchy
[{'answer': '16 March 1815', 'provenance': [{'wikipedia_id': '23416611', 'title': 'Monarchy of the Netherlands', 'start_paragraph_id': 2, 'start_character': 70, 'end_paragraph_id': 2, 'end_character': 83, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '23416611', 'title': 'Monarchy of the Netherlands', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 655, 'bleu_score': 0.9817332376369081, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9801941199293579750}, 'section': 'Section::::Abstract.'}]}]