Which Roman emperor served for the shortest time during the Principate?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'INTERNAL', 'name_': 'Q1138524', 'id': 0, 'label': 'Paulys Realenzyklopädie der klassischen Altertumswissenschaft'}, {'type': 'INTERNAL', 'name_': 'Q220', 'id': 1, 'label': 'Rome'}, {'type': 'QUESTIONS_ENTITY', 'name_': 'Q842606', 'id': 2, 'label': 'Roman emperor'}, {'type': 'INTERNAL', 'name_': 'Q2277', 'id': 3, 'label': 'Roman Empire'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q1414', 'id': 4, 'label': 'Galba'}, {'type': 'INTERNAL', 'name_': 'Q1413', 'id': 5, 'label': 'Nero'}, {'type': 'INTERNAL', 'name_': 'Q938137', 'id': 6, 'label': 'Quo Vadis'}, {'type': 'INTERNAL', 'name_': 'Q3556008', 'id': 7, 'label': 'Koinon of Free Laconians'}, {'type': 'QUESTIONS_ENTITY', 'name_': 'Q206414', 'id': 8, 'label': 'Principate'}, {'type': 'INTERNAL', 'name_': 'Q19997382', 'id': 9, 'label': 'Sulpicius 63 (Pauly-Wissowa)'}, {'type': 'INTERNAL', 'name_': 'Q113465824', 'id': 10, 'label': 'Valerian dynasty'}, {'type': 'INTERNAL', 'name_': 'Q617650', 'id': 11, 'label': 'Battle of the Medway'}], 'links': [{'name_': 'P361', 'source': 2, 'target': 3, 'label': 'part of'}, {'name_': 'P36', 'source': 3, 'target': 1, 'label': 'capital'}, {'name_': 'P1906', 'source': 3, 'target': 2, 'label': 'office held by head of state'}, {'name_': 'P1343', 'source': 5, 'target': 0, 'label': 'described by source'}, {'name_': 'P20', 'source': 5, 'target': 1, 'label': 'place of death'}, {'name_': 'P39', 'source': 5, 'target': 2, 'label': 'position held'}, {'name_': 'P840', 'source': 6, 'target': 1, 'label': 'narrative location'}, {'name_': 'P674', 'source': 6, 'target': 4, 'label': 'characters'}, {'name_': 'P674', 'source': 6, 'target': 5, 'label': 'characters'}, {'name_': 'P1343', 'source': 7, 'target': 0, 'label': 'described by source'}, {'name_': 'P131', 'source': 7, 'target': 3, 'label': 'located in the administrative territorial entity'}, {'name_': 'P2348', 'source': 7, 'target': 8, 'label': 'time period'}, {'name_': 'P361', 'source': 9, 'target': 0, 'label': 'part of'}, {'name_': 'P921', 'source': 9, 'target': 4, 'label': 'main subject'}, {'name_': 'P159', 'source': 10, 'target': 1, 'label': 'headquarters location'}, {'name_': 'P17', 'source': 10, 'target': 3, 'label': 'country'}, {'name_': 'P1454', 'source': 10, 'target': 8, 'label': 'legal form'}, {'name_': 'P710', 'source': 11, 'target': 3, 'label': 'participant'}, {'name_': 'P710', 'source': 11, 'target': 4, 'label': 'participant'}]}