Question: who plays katherine in vampire diaries season 8
[{'answer': 'Nina Dobrev', 'provenance': [{'wikipedia_id': '50959719', 'title': 'The Vampire Diaries (season 8)', 'start_paragraph_id': 48, 'start_character': 43, 'end_paragraph_id': 48, 'end_character': 54, 'bleu_score': 1.0, 'section': 'Section::::Production.:Casting.\n'}]}, {'provenance': [{'wikipedia_id': '50959719', 'title': 'The Vampire Diaries (season 8)', 'start_paragraph_id': 43, 'start_character': 0, 'end_paragraph_id': 43, 'end_character': 59, 'bleu_score': 0.725979529115477, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3485917102543829952}, 'section': 'Section::::Cast.:Guest.\n'}]}]