pyqt treeview not displaying with overloaded model

Question

I need some help with a treeview. When I specify the model as

class TreeModel(QtGui.QStandardItemModel):

    def __init__(self,parent=None):
        QtGui.QStandardItemModel.__init__(self,parent)
        self.rootItem = QtGui.QStandardItem('root')

I'm able to add items to the tree from the window with

def on_actionAddItem_triggered(self,checked=None):

    if checked is None: 
        return

    parent = self.model.invisibleRootItem()
    parent.appendRow(QtGui.QStandardItem("test"))

But when I try to overload the model, the treeview doesn't update. The code fails to update the treeview. Can someone explain please?

class TreeModel(QtGui.QStandardItemModel):

    def __init__(self,parent=None):
        QtGui.QStandardItemModel.__init__(self,parent)
        self.rootItem = QtGui.QStandardItem('root')

    def data(self,index,role):

        if role == QtCore.Qt.DisplayRole:
            row = index.row()
            text = self.rootItem.child(row)
            return text.text()

    def columnCount(self,parent=None):
        return 1

    def rowCount(self,parent=QtCore.QModelIndex()):
        return self.rootItem.rowCount()

    def headerData(self, column, orientation, role):
        if role == QtCore.Qt.DisplayRole:
            if orientation == QtCore.Qt.Horizontal:
                if column == 0:
                    return 'zero'

Answer 1

I discovered that, invisibleRootItem() does not automatically point to the root item. Simply specifying parent = self.model.rootItem resolved the issue.