load( url, onLoad, onProgress, onError ) {

		const _onError = function ( e ) {

			if ( onError ) {

				onError( e );

			} else {

				console.error( e );

			}

		};

		new FileLoader( this.manager )
			.setPath( this.path )
			.load( url, async ( text ) => {

				try {

					onLoad( this.parse( text ) );

				} catch ( e ) {

					_onError( e );

				}

			}, onProgress, _onError );

		return this;

	}
Starts loading from the given URL and passes the loaded MaterialX asset
to the `onLoad()` callback.

@param {string} url - The path/URL of the file to be loaded. This can also be a data URI.
@param {function(Object<string,NodeMaterial>)} onLoad - Executed when the loading process has been finished.
@param {onProgressCallback} onProgress - Executed while the loading is in progress.
@param {onErrorCallback} onError - Executed when errors occur.
@return {MaterialXLoader} A reference to this loader.