Who was the longest-serving congressperson?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'INTERNAL', 'name_': 'Q30', 'id': 0, 'label': 'United States of America'}, {'type': 'INTERNAL', 'name_': 'Q2341317', 'id': 1, 'label': 'John Randolph of Roanoke'}, {'type': 'QUESTIONS_ENTITY', 'name_': 'Q14761450', 'id': 2, 'label': 'member of congress'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q640835', 'id': 3, 'label': 'Jamie Raskin'}, {'type': 'INTERNAL', 'name_': 'Q6758404', 'id': 4, 'label': 'Marcus Raskin'}], 'links': [{'name_': 'P17', 'source': 0, 'target': 0, 'label': 'country'}, {'name_': 'P27', 'source': 1, 'target': 0, 'label': 'country of citizenship'}, {'name_': 'P39', 'source': 1, 'target': 2, 'label': 'position held'}, {'name_': 'P27', 'source': 4, 'target': 0, 'label': 'country of citizenship'}, {'name_': 'P40', 'source': 4, 'target': 3, 'label': 'child'}]}