ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI=1S/C4H4/c1-4-2-3-4/h2-3H,1H2/file?format=sdf&get3d=True  -- InChI=1S/C4H4/c1-4-2-3-4/h2-3H,1H2 could not be loaded.