RuntimeError in pickling

Hi Taka,
Thank you very much for sharing the code.  I am running into this problem:
dataprep.py", line 65, in main
    pickle.dump(library, file, protocol=pickle.HIGHEST_PROTOCOL)
RuntimeError: Pickling of "rdkit.Chem.rdSubstructLibrary.SubstructLibrary" instances is not enabled (http://www.boost.org/libs/python/doc/v2/pickle.html)
Best regards,
Rad.