Question: when was the national ization of indian railway done
[{'answer': '1951', 'provenance': [{'wikipedia_id': '2089820', 'title': 'Railway nationalization', 'start_paragraph_id': 18, 'start_character': 43, 'end_paragraph_id': 18, 'end_character': 47, 'bleu_score': 1.0, 'section': 'Section::::India.\n'}]}, {'provenance': [{'wikipedia_id': '2089820', 'title': 'Railway nationalization', 'start_paragraph_id': 18, 'start_character': 0, 'end_paragraph_id': 18, 'end_character': 47, 'bleu_score': 0.7598356856515921, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16053899177893744086}, 'section': 'Section::::India.\n'}]}]