distutils.version.Version:
Abstract base class for version numbering classes. Just provides
constructor (__init__) and reproducer (__repr__), because those
seem to be the same for all version numbering classes.
mvpa.mappers.base.Mapper:
Interface to provide mapping between two spaces: IN and OUT.
Methods are prefixed correspondingly. forward/reverse operate
on the entire dataset. get(In|Out)Id[s] operate per element:
mvpa.featsel.helpers.StoppingCriterion:
Base class for all functors to decide when to stop RFE (or may
be general optimization... so it probably will be moved out into
some other module