The following DataNodes have no identifier: 1
http://classic.wikipathways.org/instance/WP1074_r117577 http://rdf.wikipathways.org/Pathway/WP1074_r117577/DataNode/d68 (PDGF-BB)
More details at https://www.wikipathways.org/WikiPathwaysCurator/DataNodesTests/dataNodesWithoutIdentifier