ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI=1S/C4H4N2/c1-2-5-4-6-3-1/h1-4H/file?format=sdf&get3d=True  -- InChI=1S/C4H4N2/c1-2-5-4-6-3-1/h1-4H could not be loaded.