Question: who voiced the joker in batman the animated series
[{'answer': 'Mark Hamill', 'provenance': [{'wikipedia_id': '171478', 'title': 'Batman: The Animated Series', 'start_paragraph_id': 8, 'start_character': 142, 'end_paragraph_id': 8, 'end_character': 153, 'bleu_score': 1.0, 'section': 'Section::::Overview.\n'}]}]