ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI=1S/C4H4N2/c5-3-1-2-4-6/h1-2H2/file?format=sdf&get3d=True  -- InChI=1S/C4H4N2/c5-3-1-2-4-6/h1-2H2 could not be loaded.