The following DataNodes have no identifier: 1
http://classic.wikipathways.org/instance/WP1019_r120928 http://rdf.wikipathways.org/Pathway/WP1019_r120928/DataNode/caa (CASP10)
More details at https://www.wikipathways.org/WikiPathwaysCurator/DataNodesTests/dataNodesWithoutIdentifier