Question: who played the emperor in the empire strikes back
[{'answer': 'Ian McDiarmid', 'provenance': [{'wikipedia_id': '18426653', 'title': 'Palpatine', 'start_paragraph_id': 1, 'start_character': 270, 'end_paragraph_id': 1, 'end_character': 283, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]