The following DataNodes have no identifier: 1
http://classic.wikipathways.org/instance/WP1771_r126406 http://rdf.wikipathways.org/Pathway/WP1771_r126406/DataNode/c17ec (DAG)
More details at https://www.wikipathways.org/WikiPathwaysCurator/DataNodesTests/dataNodesWithoutIdentifier