Question: who was declared as the emperor after the revolt of 1857
[{'answer': 'Bahadur Shah Zafar', 'provenance': [{'wikipedia_id': '590246', 'title': 'Indian Rebellion of 1857', 'start_paragraph_id': 3, 'start_character': 115, 'end_paragraph_id': 3, 'end_character': 133, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '590246', 'title': 'Indian Rebellion of 1857', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 1062, 'bleu_score': 0.9534449388857791, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11726363111353467726}, 'section': 'Section::::Abstract.'}]}]