code: function getFirstNgModuleName(source) {
      // First, find the @NgModule decorators.
      const ngModulesMetadata = getDecoratorMetadata(source, 'NgModule', '@angular/core');
      if (ngModulesMetadata.length === 0) {
          return undefined;
      }
      // Then walk parent pointers up the AST, looking for the ClassDeclaration parent of the NgModule
      // metadata.
      const moduleClass = findClassDeclarationParent(ngModulesMetadata[0]);
      if (!moduleClass || !moduleClass.name) {
          return undefined;
      }
      // Get the class name of the module ClassDeclaration.
      return moduleClass.name.text;
  }
docs: Given a source file with @NgModule class(es), find the name of the first @NgModule class.
  
  @param source source file containing one or more @NgModule
  @returns the name of the first @NgModule, or `undefined` if none is found