def METHOD_NAME(package, mask):
    import fnmatch
    if (hasattr(package, "__loader__") and
            hasattr(package.__loader__, '_files')):
        path = package.__name__.replace(".", os.path.sep)
        mask = os.path.join(path, mask)
        for fnm in package.__loader__._files.iterkeys():
            if fnmatch.fnmatchcase(fnm, mask):
                yield os.path.splitext(fnm)[0].replace(os.path.sep, ".")
    else:
        path = package.__path__[0]
        for fnm in os.listdir(path):
            if fnmatch.fnmatchcase(fnm, mask):
                yield "%s.%s" % (package.__name__, os.path.splitext(fnm)[0])