wx.grid with wx.GridTableBase: col/row inserting/deleting

Hello,

Could anyone here provide a simple example of inserting/deleting cols or rows
in a wx.grid backed with a data table? The wiki cannot help, and neither can
_wxPython In Action_...

I have tried the following:

···

****************************************************************************
class GridTable(wx.grid.PyGridTableBase):

  ncols = 0
  nrows = 0
  
  <snip>
  
  def InsertCols(self, pos=1, numCols=2):
    self.ncols += numCols
    return True

***************************************************************************

But when I call, say grid.InsertCols(2, 2), nothing happens, even if I
refresh... have I missed something?

Thanks for any help.

--
Gouki
LP,LP,F,F,LK,HP