The following DataNodes have no identifier: 1
http://classic.wikipathways.org/instance/WP1040_r117545 http://rdf.wikipathways.org/Pathway/WP1040_r117545/DataNode/aca (IgM)
More details at https://www.wikipathways.org/WikiPathwaysCurator/DataNodesTests/dataNodesWithoutIdentifier