Which performing group has the most No. 1 hit songs?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'INTERNAL', 'name_': 'Q45', 'id': 0, 'label': 'Portugal'}, {'type': 'INTERNAL', 'name_': 'Q29', 'id': 1, 'label': 'Spain'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q2041543', 'id': 2, 'label': 'Ottův slovník naučný'}, {'type': 'QUESTIONS_ENTITY', 'name_': 'Q215380', 'id': 3, 'label': 'musical group'}, {'type': 'INTERNAL', 'name_': 'Q373899', 'id': 4, 'label': 'record chart'}, {'type': 'INTERNAL', 'name_': 'Q178790', 'id': 5, 'label': 'labor union'}, {'type': 'QUESTIONS_ENTITY', 'name_': 'Q20878491', 'id': 6, 'label': 'number-one hit'}, {'type': 'INTERNAL', 'name_': 'Q831044', 'id': 7, 'label': "Syndicat National de l'Édition Phonographique"}, {'type': 'INTERNAL', 'name_': 'Q8597949', 'id': 8, 'label': 'Category:Lists of number-one songs in Spain'}], 'links': [{'name_': 'P17', 'source': 0, 'target': 0, 'label': 'country'}, {'name_': 'P47', 'source': 0, 'target': 1, 'label': 'shares border with'}, {'name_': 'P1343', 'source': 0, 'target': 2, 'label': 'described by source'}, {'name_': 'P1343', 'source': 3, 'target': 2, 'label': 'described by source'}, {'name_': 'P527', 'source': 4, 'target': 6, 'label': 'has part(s)'}, {'name_': 'P1343', 'source': 5, 'target': 2, 'label': 'described by source'}, {'name_': 'P31', 'source': 7, 'target': 4, 'label': 'instance of'}, {'name_': 'P31', 'source': 7, 'target': 5, 'label': 'instance of'}, {'name_': 'P971', 'source': 8, 'target': 1, 'label': 'category combines topics'}, {'name_': 'P971', 'source': 8, 'target': 6, 'label': 'category combines topics'}]}