Question: when was the last time chelsea won fa cup
[{'answer': '2018'}, {'provenance': [{'wikipedia_id': '19887297', 'title': 'List of FA Cup Finals', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 420, 'bleu_score': 0.817384224574013, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10467393167761969409}, 'section': 'Section::::Abstract.'}]}]