ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI=1S/C6H8N2/c7-5-3-1-2-4-6-8/h1-4H2/file?format=sdf&get3d=True -- InChI=1S/C6H8N2/c7-5-3-1-2-4-6-8/h1-4H2 could not be loaded.