Question: who plays ra's al ghul in arrow
[{'answer': 'Matthew Nable', 'provenance': [{'wikipedia_id': '29026663', 'title': 'Matthew Nable', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 13, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '29026663', 'title': 'Matthew Nable', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 489, 'bleu_score': 0.976327165973018, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9694222015234283383}, 'section': 'Section::::Abstract.'}]}]