ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI=1S/C2H4N4/c3-2-4-1-5-6-2/h1H,(H3,3,4,5,6)/file?format=sdf&get3d=True  -- InChI=1S/C2H4N4/c3-2-4-1-5-6-2/h1H,(H3,3,4,5,6) could not be loaded.