private void BtnQuadrado_Click(object sender, RoutedEventArgs e)
        {
            Relationship relation = ComboBoxRelation();

            if (relation != null)
            {
                SetPair setPair = relation.Square();
                txtSaida.Text = $"{relation.Name} = {setPair.ListPairToString()} \n" +
                                $"{relation.AllClassifications()}";
            }
        }