Python PyGOobject treeview: confirm edit after move between cells with Tab key

After searching for a long time I found a solution (pretty simple) to move between cells of a treeview grid using Tab key and mantaining cells in edit mode.

Now I've got a problem: cell edit confirmation happens only after pressing Enter key. If I press Tab key a editing_canceled event appears to be triggered.

How to solve it? How to permit the data confirmation also on tab key press?

This is my event handler for treeview key-press-event:

def key_tree_Tab(self, treeview, event,namewidget):
    path, col = treeview.get_cursor() 
    ## only visible columns!! 
    columns = [c for c in treeview.get_columns() if c.get_visible()] 
    colnum = columns.index(col)     

    if event.keyval==65289:

        if colnum + 1 < len(columns): 
            next_column = columns[colnum + 1]               
            treeview.set_cursor(path,next_column,start_editing=True)                                    


        else: 
            tmodel = treeview.get_model() 
            titer = tmodel.iter_next(tmodel.get_iter(path)) 
            if titer is None: 
                titer = tmodel.get_iter_first() 
            path = tmodel.get_path(titer) 
            next_column = columns[0] 
            treeview.set_cursor(path,next_column,start_editing=True)

    return True

Thanks to all!!!!

I know this thread is long ago. I tried your code with current version of Python3 and Gtk3 and does not work. It works only with new rows. The existing rows do not tab to next cell. If I add "return True" then every cell can Tab even with existing cells, but none gets updated.