MDL NoStructs are weakly supported but not recommended:
- They will always evaluate to 'false' in matches.
- Test for Nostructs with is_nostruct(); Better yet kill 'em all, for you have NULL.
Due to a bug in OpenBabel, canonical_smiles must always ignore the second parameter and will generate SMILES without stereo information.
Disconnected structures cannot be used as queries, but can be searched. This is an OpenBabel limitation.
