Python 2.7

iter_modules (iter_importers) ->
  calls iter_importer_modules for each importer in iter_importers

iter_importers (meta_path, get_importer) ->
  returns every importer in sys.meta_path + map(get_importer, sys.path)

get_importer(path):

    returns a filtered list of sys.path_hooks for importers that can
    handle this path; if there is no match, returns ImpImporter(),
    which supplies a module iterator (ImpImporter.iter_modules) that
    relies on getmodulename.  
    
    * A path_hook is a function of (path -> Maybe importer)

iter_modules(path, get_importer, prefix) ->
  calls iter_importer_modules for each importer returned by path.map(get_importer)

iter_importer_modules(importer) ->
  returns list of (filename, ispkg) for each module understood by the importer
  * The method called depends on the class of the importer
  * The default is a generic call for "no specific importer"
  * For FILES, iter_import_modules returns a list of files whose
    extensions match those in imp.get_suffixes(), which is hard-
    coded into the interpreter.
  * MEANING: Unless your importer can handle heterogenous module
    suffixes, SourceFiles.iter_importer_modules can only find
    homogeonous modules.

This relationship issue holds for Python 2.6 as well.

Python 3.3

    The same issue holds, although now most of the extensions have been
    moved to importlib._bootstrap.

It is the relationship between
   importlib.machinery.FileFinder
and
    _iter_file_finder_modules

That's killing us.