Question: who plays richard castle in the tv series castle
[{'answer': 'Nathan Fillion', 'provenance': [{'wikipedia_id': '20522030', 'title': 'Castle (TV series)', 'start_paragraph_id': 2, 'start_character': 79, 'end_paragraph_id': 2, 'end_character': 93, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '20522030', 'title': 'Castle (TV series)', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 593, 'bleu_score': 0.979896933041101, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4689189020371109885}, 'section': 'Section::::Abstract.'}]}]