Question: who is the lead singer for iron maiden
[{'answer': 'Bruce Dickinson', 'provenance': [{'wikipedia_id': '255405', 'title': 'Bruce Dickinson', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 15, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '255405', 'title': 'Bruce Dickinson', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 306, 'bleu_score': 0.8081531368887881, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9955652009194943749}, 'section': 'Section::::Abstract.'}]}]