def on_clear(self, event):
        """
        initialize window to allow user to empty the working directory
        """
        dia = pmag_menu_dialogs.ClearWD(self.parent, self.parent.WD)
        clear = dia.do_clear()
        if clear:
            print('-I- Clear data object')
            self.contribution = cb.Contribution(self.WD, dmodel=self.data_model)
            self.edited = False
initialize window to allow user to empty the working directory