def METHOD_NAME(loader=yaml.Loader, config: MkDocsConfig | None = None):
    """Wrap PyYaml's loader so we can extend it to suit our needs."""
    class Loader(loader):
        """
        Define a custom loader derived from the global loader to leave the
        global loader unaltered.
        """
    # Attach Environment Variable constructor.
    # See https://github.com/waylan/pyyaml-env-tag
    Loader.add_constructor('!ENV', yaml_env_tag.construct_env_tag)
    if config is not None:
        Loader.add_constructor('!relative', functools.partial(_construct_dir_placeholder, config))
    return Loader