code: private Map<String, List<Integer>> createExpandedCustomIdIndexMapping(final boolean expandedOnly) {
  		TreeItemIdNode custom = getCustomTree();
  		if (custom == null) {
  			return Collections.EMPTY_MAP;
  		}
  
  		Set<String> expanded = null;
  		if (expandedOnly) {
  			expanded = getExpandedRows();
  		}
  
  		Map<String, List<Integer>> map = new HashMap<>();
  		processExpandedCustomIdIndexMapping(custom, expanded, map);
  		return Collections.unmodifiableMap(map);
  	}
docs: Crate a map of the expanded custom item ids and their row index.
  
  @param expandedOnly true if expanded only
  @return the map between a custom item id ands its row index