Question: what is the name of beethoven's only opera
[{'answer': 'Fidelio', 'provenance': [{'wikipedia_id': '38475', 'title': 'Fidelio', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 7, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '38475', 'title': 'Fidelio', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 593, 'bleu_score': 0.853375950141629, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7318315178964466292}, 'section': 'Section::::Abstract.'}]}]