def declare_namespace(packageName):
    """Declare that package 'packageName' is a namespace package"""

    _imp.acquire_lock()
    try:
        if packageName in _namespace_packages:
            return

        path = sys.path
        parent, _, _ = packageName.rpartition('.')

        if parent:
            declare_namespace(parent)
            if parent not in _namespace_packages:
                __import__(parent)
            try:
                path = sys.modules[parent].__path__
            except AttributeError:
                raise TypeError("Not a package:", parent)

        # Track what packages are namespaces, so when new path items are added,
        # they can be updated
        _namespace_packages.setdefault(parent or None, []).append(packageName)
        _namespace_packages.setdefault(packageName, [])

        for path_item in path:
            # Ensure all the parent's path items are reflected in the child,
            # if they apply
            _handle_ns(packageName, path_item)

    finally:
        _imp.release_lock()
Declare that package 'packageName' is a namespace package
product/gradle-plugin/src/main/python/pip/_vendor/pkg_resources/__init__.py