Question: where did the tradition of flying flags at half mast come from
[{'answer': '17th century', 'provenance': [{'wikipedia_id': '1617234', 'title': 'Half-mast', 'start_paragraph_id': 2, 'start_character': 60, 'end_paragraph_id': 2, 'end_character': 72, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '1617234', 'title': 'Half-mast', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 741, 'bleu_score': 0.9278524488917361, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6275945678790518908}, 'section': 'Section::::Abstract.'}]}]