Question: who played robbie douglas in my three sons
[{'answer': 'Don Grady', 'provenance': [{'wikipedia_id': '174002', 'title': 'My Three Sons', 'start_paragraph_id': 13, 'start_character': 647, 'end_paragraph_id': 13, 'end_character': 656, 'bleu_score': 1.0, 'section': 'Section::::History.:CBS years.\n'}]}]