event called pressing on ENTER key.

        propagates the string content of the input field

def on_keydown_listener(self, widget, value, keycode):
        """event called pressing on ENTER key.

        propagates the string content of the input field
        """
        if keycode=="13":
            self.hide()
            self.inputText.set_text(value)
            self.confirm_value(self)