How to use the @iiif/vocabulary.ExternalResourceType.PHYSICAL_OBJECT function in @iiif/vocabulary

this._extensionRegistry = {};

        this._extensionRegistry[ExternalResourceType.CANVAS] = {
            load: this._extensions[Extension.OSD]
        };

        this._extensionRegistry[ExternalResourceType.IMAGE] = {
            load: this._extensions[Extension.OSD]
        };

        this._extensionRegistry[ExternalResourceType.MOVING_IMAGE] = {
            load: this._extensions[Extension.MEDIAELEMENT]
        };

        this._extensionRegistry[ExternalResourceType.PHYSICAL_OBJECT] = {
            load: this._extensions[Extension.VIRTEX]
        };

        this._extensionRegistry[ExternalResourceType.SOUND] = {
            load: this._extensions[Extension.MEDIAELEMENT]
        };

        this._extensionRegistry[RenderingFormat.PDF] = {
            load: this._extensions[Extension.PDF]
        };

        // presentation 3

        this._extensionRegistry[MediaType.JPG] = {
            load: this._extensions[Extension.OSD]
        };