Question: when did the battle of vimy ridge end
[{'answer': '12 April 1917', 'provenance': [{'wikipedia_id': '70435', 'title': 'Battle of Vimy Ridge', 'start_paragraph_id': 1, 'start_character': 295, 'end_paragraph_id': 1, 'end_character': 308, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]