code: function registerModuleFactory(id, factory) {
      var existing = moduleFactories.get(id);
      if (existing) {
          throw new Error("Duplicate module registered for " + id + " - " + existing.moduleType.name + " vs " + factory.moduleType.name);
      }
      moduleFactories.set(id, factory);
  }
docs: Registers a loaded module. Should only be called from generated NgModuleFactory code.
  @experimental