What was the highest rated Steam game of all time in terms of concurrent players?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'INTERNAL', 'name_': 'Q193581', 'id': 0, 'label': 'Half-Life 2'}, {'type': 'QUESTIONS_ENTITY', 'name_': 'Q337535', 'id': 1, 'label': 'Steam'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q54820071', 'id': 2, 'label': 'digital download'}], 'links': [{'name_': 'P750', 'source': 0, 'target': 1, 'label': 'distributed by'}, {'name_': 'P437', 'source': 0, 'target': 2, 'label': 'distribution format'}]}