What is the name of the second largest volcano in the world?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'QUESTIONS_ENTITY', 'name_': 'Q8072', 'id': 0, 'label': 'volcano'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q102904', 'id': 1, 'label': 'volcanology'}, {'type': 'INTERNAL', 'name_': 'Q57896639', 'id': 2, 'label': 'Great challenges in volcanology: how does the volcano factory work?'}], 'links': [{'name_': 'P921', 'source': 2, 'target': 0, 'label': 'main subject'}, {'name_': 'P921', 'source': 2, 'target': 1, 'label': 'main subject'}]}