Question: in which year did the british parliament prohibit the buying and selling of slaves
[{'answer': '1807', 'provenance': [{'wikipedia_id': '498157', 'title': 'Slave Trade Act 1807', 'start_paragraph_id': 0, 'start_character': 16, 'end_paragraph_id': 0, 'end_character': 20, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '498157', 'title': 'Slave Trade Act 1807', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 331, 'bleu_score': 0.9224532597476071, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5840089937222840754}, 'section': 'Section::::Abstract.'}]}]