def METHOD_NAME():
    """Test :func:`~astropy.cosmology._io.yaml.yaml_representer`."""
    # test function `representer`
    representer = yaml_representer("!astropy.cosmology.flrw.LambdaCDM")
    assert callable(representer)
    # test the normal method of dumping to YAML
    yml = dump(Planck18)
    assert isinstance(yml, str)
    assert yml.startswith("!astropy.cosmology.flrw.FlatLambdaCDM")