The following DataNodes have no identifier: 1
http://classic.wikipathways.org/instance/WP1010_r120483 http://rdf.wikipathways.org/Pathway/WP1010_r120483/DataNode/d77d4 (Groucho)
More details at https://www.wikipathways.org/WikiPathwaysCurator/DataNodesTests/dataNodesWithoutIdentifier