def _paths(cls, fullname):
        # Ensure __path__ is not empty for the spec to be considered a namespace.
        return NAMESPACES[fullname] or MAPPING.get(fullname) or [PATH_PLACEHOLDER]

    @classmethod
    def find_spec(cls, fullname, target=None):
        if fullname in NAMESPACES:
            spec = ModuleSpec(fullname, None, is_package=True)
            spec.submodule_search_locations = cls._paths(fullname)
            return spec
        return None

    @classmethod
    def find_module(cls, fullname):
        return None


def install():
    if not any(finder == _EditableFinder for finder in sys.meta_path):
        sys.meta_path.append(_EditableFinder)

    if not NAMESPACES:
        return

    if not any(hook == _EditableNamespaceFinder._path_hook for hook in sys.path_hooks):
        # PathEntryFinder is needed to create NamespaceSpec without private APIS
        sys.path_hooks.append(_EditableNamespaceFinder._path_hook)
    if PATH_PLACEHOLDER not in sys.path:
        sys.path.append(PATH_PLACEHOLDER)  # Used just to trigger the path hook
ri