Remove all inplace edit widgets.

def __clear_inplace_widgets(self):
        """Remove all inplace edit widgets."""
        cols = self.__get_display_columns()
        #print('Clear:', cols)
        for c in cols:
            if c in self._inplace_widgets:
                widget = self._inplace_widgets[c]
                widget.place_forget()
                self._inplace_widgets_show.pop(c, None)