Question: when was the first episode of pretty little liars filmed
[{'answer': 'Vancouver', 'provenance': [{'wikipedia_id': '28733477', 'title': 'Pilot (Pretty Little Liars)', 'start_paragraph_id': 15, 'start_character': 28, 'end_paragraph_id': 15, 'end_character': 37, 'bleu_score': 1.0, 'section': 'Section::::Production.:Filming.\n'}]}, {'provenance': [{'wikipedia_id': '28733477', 'title': 'Pilot (Pretty Little Liars)', 'start_paragraph_id': 15, 'start_character': 0, 'end_paragraph_id': 15, 'end_character': 216, 'bleu_score': 0.950578622812921, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2829855822999975148}, 'section': 'Section::::Production.:Filming.\n'}]}]