Question: who did the soviet union signed a nonaggression pact with in 1939
[{'answer': 'Nazi Germany', 'provenance': [{'wikipedia_id': '20950', 'title': 'Molotov–Ribbentrop Pact', 'start_paragraph_id': 1, 'start_character': 169, 'end_paragraph_id': 1, 'end_character': 181, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]