The following DataNodes have no identifier: 2
http://classic.wikipathways.org/instance/WP4504_rr119316 http://rdf.wikipathways.org/Pathway/WP4504_rr119316/DataNode/ed273 (ST)
http://classic.wikipathways.org/instance/WP4504_rr119316 http://rdf.wikipathways.org/Pathway/WP4504_rr119316/DataNode/f21ac (Transsulfuration pathway)