URDF model didn't appear in three.js

Question

When I try to visualize a urdf model in the three.js, it doesn't appear.

Using module https://github.com/gkjohnson/urdf-loaders/blob/master/javascript/README.md

import { GLTFLoader } from 'three/examples/loaders/GLTFLoader.js';
import URDFLoader from 'urdf-loader';

// ...init three.js scene...

const loader = new URDFLoader();
loader.loadMeshCb = function( path, manager, onComplete ) {

    const gltfLoader = new GLTFLoader( manager );
    gltfLoader.load(
        path,
        result => {

            onComplete( result.scene );

        },
        undefined,
        err => {
        
            // try to load again, notify user, etc
        
            onComplete( null, err );
        
        }
    );

};
loader.load( 'T12/urdf/T12.URDF', robot => {

    // The robot is loaded!
    scene.add( robot );

} );