Question: who plays the voice of wheatley in portal 2
[{'answer': 'Stephen Merchant', 'provenance': [{'wikipedia_id': '31592759', 'title': 'Wheatley (Portal)', 'start_paragraph_id': 1, 'start_character': 161, 'end_paragraph_id': 1, 'end_character': 177, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '31592759', 'title': 'Wheatley (Portal)', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 234, 'bleu_score': 0.855530866466304, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10899963511800363102}, 'section': 'Section::::Abstract.'}]}]