ERROR opening https://cactus.nci.nih.gov/chemical/structure/C1%3DCN%3DC%28N%3DC1%29C2%3DNC%3DCC%3DN2/file?format=sdf&get3d=True -- C1%3DCN%3DC%28N%3DC1%29C2%3DNC%3DCC%3DN2 could not be loaded.