How to use the blessed-contrib.createScreen function in blessed-contrib

if (err) {
         return cba("Document xml is not valid: " + err)
      }
    
      if (!doc || !doc.document) return cba("document not valid or has no pages")
      if (!doc.document.page || doc.document.page.length==0) return cba("document must have at least one page")
      
      if (page>=doc.document.page.length) {
         return cba('\r\n\r\nPresentation has ended (total '+doc.document.page.length+' pages). Press CTRL+C to exit.\r\n\r\n')
      }
      
      req.connection.on('close',function(){
        screen = null
      });
      
      var screen = contrib.createScreen(req, res)
      if (screen==null) return
      
      viewer = new Viewer(doc.document, screen)
      var err = viewer.renderPage(page, msg)
      if (err!==null) {
        clean(screen)
        return cba(err)
      }
      
      //note the setTimeout is necessary even if delay is 0
      setTimeout(function() {
        //restore cursor
        res.end('\033[?25h')
        clean(screen)
        return cba()
      }, auto?5000:0)