How to use the pscript.stubs.window.document.createElement function in pscript

window.flexx.spin()
            address = window.location.protocol + '//' + self.ws_url.split('/')[2]
            code += '\n//# sourceURL=%s/flexx/assets/shared/%s\n' % (address, name)
            if kind == 'JS-EVAL':
                eval(code)
            elif kind == 'JS':
                # With this method, sourceURL does not work on Firefox,
                # but eval might not work for assets that don't "use strict"
                # (e.g. Bokeh). Note, btw, that creating links to assets does
                # not work because these won't be loaded on time.
                el = window.document.createElement("script")
                el.id = name
                el.innerHTML = code
                window.flexx.asset_node.appendChild(el)
            elif kind == 'CSS':
                el = window.document.createElement("style")
                el.type = "text/css"
                el.id = name
                el.innerHTML = code
                window.flexx.asset_node.appendChild(el)
            else:
                window.console.error('Dont know how to DEFINE ' +
                                     name + ' with "' + kind + '".')
        elif cmd == 'OPEN':
            window.win1 = window.open(command[1], 'new', 'chrome')
        else:
            window.console.error('Invalid command: "' + cmd + '"')
        return command

elif cmd == 'DISPOSE_ACK':
            self.instances.pop(command[1], None)  # Drop reference
        elif cmd == 'DEFINE':
            #and command[1] == 'JS' or command[1] == 'DEFINE-JS-EVAL '):
            kind, name, code = command[1:]
            window.flexx.spin()
            address = window.location.protocol + '//' + self.ws_url.split('/')[2]
            code += '\n//# sourceURL=%s/flexx/assets/shared/%s\n' % (address, name)
            if kind == 'JS-EVAL':
                eval(code)
            elif kind == 'JS':
                # With this method, sourceURL does not work on Firefox,
                # but eval might not work for assets that don't "use strict"
                # (e.g. Bokeh). Note, btw, that creating links to assets does
                # not work because these won't be loaded on time.
                el = window.document.createElement("script")
                el.id = name
                el.innerHTML = code
                window.flexx.asset_node.appendChild(el)
            elif kind == 'CSS':
                el = window.document.createElement("style")
                el.type = "text/css"
                el.id = name
                el.innerHTML = code
                window.flexx.asset_node.appendChild(el)
            else:
                window.console.error('Dont know how to DEFINE ' +
                                     name + ' with "' + kind + '".')
        elif cmd == 'OPEN':
            window.win1 = window.open(command[1], 'new', 'chrome')
        else:
            window.console.error('Invalid command: "' + cmd + '"')

def init(self):
        """ Called after document is loaded. """
        # Create div to put dynamic CSS assets in
        self.asset_node = window.document.createElement("div")
        self.asset_node.id = 'Flexx asset container'
        window.document.body.appendChild(self.asset_node)

        if self.is_exported:
            if self.is_notebook:
                print('Flexx: I am in an exported notebook!')
            else:
                print('Flexx: I am in an exported app!')
                self.run_exported_app()
        else:
            print('Flexx: Initializing')
            if not self.is_notebook:
                self._remove_querystring()
            self.init_logging()