I remember once getting a comment that nested functions prevent picklability, I don't remember exactly, but it works fine in this case.  Is it an older python thing?  @GaelVaroquaux @ogrisel @jnothman could anybody please clarify?

Also I have the impression that because both spectral biclustering objects are simply estimators but neither transformers, classifiers nor regressors, there is no common tests for their picklability.