Can’t make child in Qtreeview using QStandardItemModel

[umen]

after reading some examples i still missing here something . i have Qtreeview for view and QStandardItemModel for the data interface , also using QSortFilterProxyModel subclass but i dont know if its relevant. this is my logic :
first i create the model with the QWidget as the parent :

QStandardItemModel m_model = new QStandardItemModel(0,4,parent);
then setSourceModel(m_model) for the widget
set the treeview with QSortFilterProxyModel. something like this :
GroupProxyModel = new GroupSortFilterProxyModel;
GroupProxyModel->setDynamicSortFilter(true);
setSourceModel(createSubjectModel(parent));

ui.treeView_mainwindow->setModel(GroupProxyModel);
ui.treeView_mainwindow->setSortingEnabled(true);
then later i fill the first row like this :

QList<QStandardItem *> items;
items.insert(0,new QStandardItem("Test 0"));
items.at(0)->setEditable(false);
m_model->insertRow(0,items);
until now every thing working fine and i see the row with the data . but when i like to
add child to the row like this :

QModelIndex parentQModelIndex = m_model->item(0,0)->index();
m_model->insertRows(0,1,parentQModelIndex);
m_model->insertColumns(0,1,parentQModelIndex);
QModelIndex indexB = m_model->index(0, 0, parentQModelIndex);
m_model->setData(indexB,"Child test",Qt::DisplayRole);
but i dont see the child , why ?