ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI%3DInChI%26%2361%3B1S/C4H4N2/c1-2-6-4-3-5-1/h1-4H/file?format=sdf&get3d=True  -- InChI%3DInChI%26%2361%3B1S/C4H4N2/c1-2-6-4-3-5-1/h1-4H could not be loaded.