Question: who plays the voice of mabel on gravity falls
[{'answer': 'Kristen Joy Schaal', 'provenance': [{'wikipedia_id': '7297505', 'title': 'Kristen Schaal', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 18, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]