Question: what was the purpose of the elmina castle
[{'answer': 'a trade settlement', 'provenance': [{'wikipedia_id': '1442216', 'title': 'Elmina Castle', 'start_paragraph_id': 1, 'start_character': 363, 'end_paragraph_id': 1, 'end_character': 381, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '1442216', 'title': 'Elmina Castle', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 774, 'bleu_score': 0.8828469500433931, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16202110105696532585}, 'section': 'Section::::Abstract.'}]}]