code: function addUserAddedCatalog(terria, initSources) {
    const localDataFilterRemembering = rememberRejections(
      CatalogMember.itemFilters.noLocalData
    );
  
    const userAddedCatalog = terria.catalog.serializeToJson({
      itemFilter: combineFilters([
        localDataFilterRemembering.filter,
        CatalogMember.itemFilters.userSuppliedOnly,
        function(item) {
          // If the parent has a URL then this item will just load from that, so don't bother serializing it.
          // Properties that change when an item is enabled like opacity will be included in the shared members
          // anyway.
          return !item.parent || !item.parent.url;
        }
      ])
    });
  
    // Add an init source with user-added catalog members.
    if (userAddedCatalog.length > 0) {
      initSources.push({
        catalog: userAddedCatalog
      });
    }
  
    return localDataFilterRemembering.rejections;
  }
docs: Adds user-added catalog members to the passed initSources.
  @private