Question: when was the maple leaf first adopted as a symbol in canada
[{'answer': '1868', 'provenance': [{'wikipedia_id': '97066', 'title': 'Flag of Canada', 'start_paragraph_id': 7, 'start_character': 116, 'end_paragraph_id': 7, 'end_character': 120, 'bleu_score': 1.0, 'section': 'Section::::Origins and design.\n'}]}, {'provenance': [{'wikipedia_id': '97066', 'title': 'Flag of Canada', 'start_paragraph_id': 7, 'start_character': 0, 'end_paragraph_id': 7, 'end_character': 798, 'bleu_score': 0.9860618656782161, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17472858584421299608}, 'section': 'Section::::Origins and design.\n'}]}]