Question: where does the blood in the pulmonary vein come from
[{'answer': 'the lungs', 'provenance': [{'wikipedia_id': '601365', 'title': 'Pulmonary vein', 'start_paragraph_id': 1, 'start_character': 70, 'end_paragraph_id': 1, 'end_character': 79, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '601365', 'title': 'Pulmonary vein', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 281, 'bleu_score': 0.958740481558872, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 515222190412510232}, 'section': 'Section::::Abstract.'}]}]