'Internal method
This method controls the undo mechanism and
the modified flag. The exact behavior of the
command depends on the option argument that
follows the edit argument. The following forms
of the command are currently supported:
edit_modified, edit_redo, edit_reset, edit_separator
and edit_undo'

def edit(self, *args):

    return self.tk.call(self._w, 'edit', *args)
