Question: when did the british empire become the british commonwealth
[{'answer': '1931', 'provenance': [{'wikipedia_id': '4721', 'title': 'British Empire', 'start_paragraph_id': 73, 'start_character': 727, 'end_paragraph_id': 73, 'end_character': 731, 'bleu_score': 1.0, 'section': 'Section::::World wars (1914–1945).:Inter-war period.\n'}]}, {'provenance': [{'wikipedia_id': '4721', 'title': 'British Empire', 'start_paragraph_id': 73, 'start_character': 0, 'end_paragraph_id': 73, 'end_character': 1302, 'bleu_score': 0.9720044292532041, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7195191932900808471}, 'section': 'Section::::World wars (1914–1945).:Inter-war period.\n'}]}]