Question: when was the last time slavery was legal
[{'answer': 'December 6 , 1865', 'provenance': [{'wikipedia_id': '253264', 'title': 'Slavery in the United States', 'start_paragraph_id': 236, 'start_character': 106, 'end_paragraph_id': 236, 'end_character': 123, 'bleu_score': 1.0, 'section': 'Section::::Civil War and emancipation.:End of slavery.\n'}]}, {'provenance': [{'wikipedia_id': '253264', 'title': 'Slavery in the United States', 'start_paragraph_id': 236, 'start_character': 0, 'end_paragraph_id': 236, 'end_character': 207, 'bleu_score': 0.527346815173938, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3204416196442320992}, 'section': 'Section::::Civil War and emancipation.:End of slavery.\n'}]}]