"""
****
YAML
****
Read and write NetworkX graphs in YAML format.

"YAML is a data serialization format designed for human readability
and interaction with scripting languages."
See http://www.yaml.org for documentation.

Format
------
http://pyyaml.org/wiki/PyYAML

"""


def __dir__():
    return ["read_yaml", "write_yaml"]


def __getattr__(name):
    """Remove functions and provide informative error messages."""
    if name == "nx_yaml":
        raise ImportError(
            "\nThe nx_yaml module has been removed from NetworkX.\n"
            "Please use the `yaml` package directly for working with yaml data.\n"
            "For example, a networkx.Graph `G` can be written to and loaded\n"
            "from a yaml file with:\n\n"
            "    import yaml\n\n"
            "    with open('path_to_yaml_file', 'w') as fh:\n"
            "        yaml.dump(G, fh)\n"
            "    with open('path_to_yaml_file', 'r') as fh:\n"
            "        G = yaml.load(fh, Loader=yaml.Loader)\n\n"
            "Note that yaml.Loader is considered insecure - see the pyyaml\n"
            "documentation for further details.\n\n"
            "This message will be removed in NetworkX 3.0."
        )
    if name == "read_yaml":
        raise ImportError(
            "\nread_yaml has been removed from NetworkX, please use `yaml`\n"
            "directly:\n\n"
            "    import yaml\n\n"
            "    with open('path', 'r') as fh:\n"
            "        yaml.load(fh, Loader=yaml.Loader)\n\n"
            "Note that yaml.Loader is considered insecure - see the pyyaml\n"
            "documentation for further details.\n\n"
            "This message will be removed in NetworkX 3.0."
        )
    if name == "write_yaml":
        raise ImportError(
            "\nwrite_yaml has been removed from NetworkX, please use `yaml`\n"
            "directly:\n\n"
            "    import yaml\n\n"
            "    with open('path_for_yaml_output', 'w') as fh:\n"
            "        yaml.dump(G_to_be_yaml, fh)\n\n"
            "This message will be removed in NetworkX 3.0."
        )
    raise AttributeError(f"module {__name__} has no attribute {name}")
