Question: when does the heart of darkness take place
[{'answer': '1899', 'provenance': [{'wikipedia_id': '13535', 'title': 'Heart of Darkness', 'start_paragraph_id': 1, 'start_character': 19, 'end_paragraph_id': 1, 'end_character': 23, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]