Who has won the most Australian Open singles titles?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'INTERNAL', 'name_': 'Q5', 'id': 0, 'label': 'human'}, {'type': 'QUESTIONS_ENTITY', 'name_': 'Q60874', 'id': 1, 'label': 'Australian Open'}, {'type': 'INTERNAL', 'name_': 'Q13538', 'id': 2, 'label': 'Henri Kontinen'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q6562732', 'id': 3, 'label': 'list of Australian Open singles finalists during the open era'}], 'links': [{'name_': 'P31', 'source': 2, 'target': 0, 'label': 'instance of'}, {'name_': 'P2522', 'source': 2, 'target': 1, 'label': 'victory'}, {'name_': 'P360', 'source': 3, 'target': 0, 'label': 'is a list of'}]}