code: public ContentsId getOrCreate(String tableName) {
  		ContentsId contentsId = get(tableName);
  		if (contentsId == null) {
  			contentsId = create(tableName);
  		}
  		return contentsId;
  	}
docs: Get or create a contents id
  
  @param tableName
  table name
  @return new or existing contents id