The following DataNodes have no identifier: 1
http://classic.wikipathways.org/instance/WP1048_r117630 http://rdf.wikipathways.org/Pathway/WP1048_r117630/DataNode/f6a (EGF)
More details at https://www.wikipathways.org/WikiPathwaysCurator/DataNodesTests/dataNodesWithoutIdentifier