code: def _setProperty(self, _type, data, win=None, mask=None):
          
          if not win:
              win = self.root
          if type(data) is str:
              dataSize = 8
          else:
              data = (data+[0]*(5-len(data)))[:5]
              dataSize = 32
  
          ev = protocol.event.ClientMessage(
              window=win,
              client_type=self.display.get_atom(_type), data=(dataSize, data))
  
          if not mask:
              mask = (X.SubstructureRedirectMask | X.SubstructureNotifyMask)
          self.root.send_event(ev, event_mask=mask)
docs: Send a ClientMessage event to the root window