Question: when did builders stop using knob and tube
[{'answer': '1930s'}, {'provenance': [{'wikipedia_id': '5444091', 'title': 'Knob-and-tube wiring', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 903, 'bleu_score': 0.9671679735406701, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7268742678965099614}, 'section': 'Section::::Abstract.'}]}]