[$] Python and public APIs

In theory, the public API of a Python standard library module is fullyspecified as part of its documentation, but in practice it may not be quite so clear cut. There are other ways to specify the names in a module thatare meant to be public, and there are naming conventions for things thatshould not be public (e.g. the name starts with an underscore), butthere is no real consistency in how those are used throughout the standard library.A mid-July discussion on the python-dev mailing list considered the problem and some possiblesolutions; the main outcome seems to be interest in making the rules moreexplicit.