How to use the @bentley/imodeljs-backend.IModelDb.rootSubjectId function in @bentley/imodeljs-backend

private createAnalysisModel(polyface: any, categoryId: Id64String, modelName: string, displacementScale = 1.0): Id64String {
    const modelId = PhysicalModel.insert(this.iModelDb, IModelDb.rootSubjectId, modelName);

    /** generate a geometry stream containing the polyface */
    const geometry = this.generateGeometryStreamFromPolyface(polyface);

    /** generate DisplayStyles to view the PolyfaceAuxData.  The display styles contain channel selection and gradient specification for the [[PolyfaceAuxData]]
     */
    const analysisStyleProps = this.getPolyfaceAnalysisStyleProps(polyface, displacementScale);
    const vf = new ViewFlags();
    const bgColor = ColorDef.white;             // White background...
    vf.renderMode = RenderMode.SolidFill;        // SolidFill rendering ... no lighting etc.

    /** The [[GeometricElement3dProps]]  */
    const props: GeometricElement3dProps = {
      model: modelId,
      code: Code.createEmpty(),
      classFullName: "Generic:PhysicalObject",

public async create(): Promise {
    this.definitionModelId = DefinitionModel.insert(this.iModelDb, IModelDb.rootSubjectId, "Definitions");
    this.physicalModelId = PhysicalModel.insert(this.iModelDb, IModelDb.rootSubjectId, "Empty Model");

    let geoLocated = false;
    const worldRange = new Range3d();
    const realityModels: ContextRealityModelProps[] = [];
    requestPromise(this.url, { json: true }).then((json: any) => {
      if (this.url.endsWith("_AppData.json")) {
        const nameIndex = this.url.lastIndexOf("TileSets");
        const prefix = this.url.substr(0, nameIndex);
        let worldToEcef: Transform | undefined;
        for (const modelValue of Object.values(json.models)) {
          const model = modelValue as any;
          if (model.tilesetUrl !== undefined &&
            model.type === "spatial") {
            let modelUrl = prefix + model.tilesetUrl.replace(/\/\//g, "/");
            modelUrl = modelUrl.replace(/ /g, "%20");
            const ecefRange = Range3d.fromJSON(model.extents);

public async import(): Promise {
    const categoryName = this._modelName ? this._modelName : "GeoJson Category";
    const modelName = this._modelName ? this._modelName : "GeoJson Model";

    let featureModelExtents: AxisAlignedBox3d;
    if (this._appendToExisting) {
      this.physicalModelId = PhysicalModel.insert(this.iModelDb, IModelDb.rootSubjectId, modelName);
      const foundCategoryId = SpatialCategory.queryCategoryIdByName(this.iModelDb, IModel.dictionaryId, categoryName);
      this.featureCategoryId = (foundCategoryId !== undefined) ? foundCategoryId : this.addCategoryToExistingDb(categoryName);
      this.convertFeatureCollection();
      const featureModel: SpatialModel = this.iModelDb.models.getModel(this.physicalModelId) as SpatialModel;
      featureModelExtents = featureModel.queryExtents();
      const projectExtents = Range3d.createFrom(this.iModelDb.projectExtents);
      projectExtents.extendRange(featureModelExtents);
      this.iModelDb.updateProjectExtents(projectExtents);
    } else {
      this.definitionModelId = DefinitionModel.insert(this.iModelDb, IModelDb.rootSubjectId, "GeoJSON Definitions");
      this.physicalModelId = PhysicalModel.insert(this.iModelDb, IModelDb.rootSubjectId, modelName);
      this.featureCategoryId = SpatialCategory.insert(this.iModelDb, this.definitionModelId, categoryName, { color: ColorDef.white });
      /** To geo-locate the project, we need to first scan the GeoJSon and extract range. This would not be required
       * if the bounding box was directly available.
       */
      const featureMin = new Cartographic(), featureMax = new Cartographic();

public async create(): Promise {
    this.definitionModelId = DefinitionModel.insert(this.iModelDb, IModelDb.rootSubjectId, "Definitions");
    this.physicalModelId = PhysicalModel.insert(this.iModelDb, IModelDb.rootSubjectId, "Empty Model");

    let geoLocated = false;
    const worldRange = new Range3d();
    const realityModels: ContextRealityModelProps[] = [];
    requestPromise(this.url, { json: true }).then((json: any) => {
      if (this.url.endsWith("_AppData.json")) {
        const nameIndex = this.url.lastIndexOf("TileSets");
        const prefix = this.url.substr(0, nameIndex);
        let worldToEcef: Transform | undefined;
        for (const modelValue of Object.values(json.models)) {
          const model = modelValue as any;
          if (model.tilesetUrl !== undefined &&
            model.type === "spatial") {
            let modelUrl = prefix + model.tilesetUrl.replace(/\/\//g, "/");
            modelUrl = modelUrl.replace(/ /g, "%20");

const modelName = this._modelName ? this._modelName : "GeoJson Model";

    let featureModelExtents: AxisAlignedBox3d;
    if (this._appendToExisting) {
      this.physicalModelId = PhysicalModel.insert(this.iModelDb, IModelDb.rootSubjectId, modelName);
      const foundCategoryId = SpatialCategory.queryCategoryIdByName(this.iModelDb, IModel.dictionaryId, categoryName);
      this.featureCategoryId = (foundCategoryId !== undefined) ? foundCategoryId : this.addCategoryToExistingDb(categoryName);
      this.convertFeatureCollection();
      const featureModel: SpatialModel = this.iModelDb.models.getModel(this.physicalModelId) as SpatialModel;
      featureModelExtents = featureModel.queryExtents();
      const projectExtents = Range3d.createFrom(this.iModelDb.projectExtents);
      projectExtents.extendRange(featureModelExtents);
      this.iModelDb.updateProjectExtents(projectExtents);
    } else {
      this.definitionModelId = DefinitionModel.insert(this.iModelDb, IModelDb.rootSubjectId, "GeoJSON Definitions");
      this.physicalModelId = PhysicalModel.insert(this.iModelDb, IModelDb.rootSubjectId, modelName);
      this.featureCategoryId = SpatialCategory.insert(this.iModelDb, this.definitionModelId, categoryName, { color: ColorDef.white });
      /** To geo-locate the project, we need to first scan the GeoJSon and extract range. This would not be required
       * if the bounding box was directly available.
       */
      const featureMin = new Cartographic(), featureMax = new Cartographic();
      if (!this.getFeatureRange(featureMin, featureMax))
        return;
      const featureCenter = new Cartographic((featureMin.longitude + featureMax.longitude) / 2, (featureMin.latitude + featureMax.latitude) / 2);

      this.iModelDb.setEcefLocation(EcefLocation.createFromCartographicOrigin(featureCenter));
      this.convertFeatureCollection();

      const featureModel: SpatialModel = this.iModelDb.models.getModel(this.physicalModelId) as SpatialModel;
      featureModelExtents = featureModel.queryExtents();
      if (!this._classifiedURL)
        this.insertSpatialView("Spatial View", featureModelExtents);