The following DataNodes have no identifier: 1
http://classic.wikipathways.org/instance/WP1029_r122565 http://rdf.wikipathways.org/Pathway/WP1029_r122565/DataNode/c16 (TNF)
More details at https://www.wikipathways.org/WikiPathwaysCurator/DataNodesTests/dataNodesWithoutIdentifier