ERROR opening https://cactus.nci.nih.gov/chemical/structure/N%3DC%28N%29N%28N%29/N%3DN/C1%3DNNN%3DN1/file?format=sdf&get3d=True  -- N%3DC%28N%29N%28N%29/N%3DN/C1%3DNNN%3DN1 could not be loaded.