def file_ns_handler(importer, path_item, packageName, module):
    """Compute an ns-package subpath for a filesystem or zipfile importer"""

    subpath = os.path.join(path_item, packageName.split('.')[-1])
    normalized = _normalize_cached(subpath)
    for item in module.__path__:
        if _normalize_cached(item) == normalized:
            break
    else:
        # Only return the path if it's not already there
        return subpath
Compute an ns-package subpath for a filesystem or zipfile importer