ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI=1S/C2H4N4/c3-1-6-2(4)5/h(H4,4,5,6)/file?format=sdf&get3d=True  -- InChI=1S/C2H4N4/c3-1-6-2(4)5/h(H4,4,5,6) could not be loaded.