code: def onkeydown(self, key, keycode, ctrl, shift, alt):
          
          return (key, keycode, ctrl, shift, alt)
docs: Called when user types and releases a key.
          The widget should be able to receive the focus in order to emit the event.
          Assign a 'tabindex' attribute to make it focusable.
          
          Args:
              key (str): the character value
              keycode (str): the numeric char code