def get_default_description(arg: inspect.Parameter) -> str:
    """
    Builds a default description for a parameter that was not documented.

    Args:
        arg (`inspect.Parameter`): The argument in the signature to generate a description for.

    Returns:
        `str`: The description.
    """
    if arg.annotation is inspect._empty:
        arg_type = "<fill_type>"
    elif hasattr(arg.annotation, "__name__"):
        arg_type = arg.annotation.__name__
    else:
        arg_type = str(arg.annotation)

    if arg.default is inspect._empty:
        return f"`{arg_type}`"
    elif arg.default is None:
        return f"`{arg_type}`, {OPTIONAL_KEYWORD}"
    else:
        str_default = stringify_default(arg.default)
        return f"`{arg_type}`, {OPTIONAL_KEYWORD}, defaults to {str_default}"

    Builds a default description for a parameter that was not documented.

    Args:
        arg (`inspect.Parameter`): The argument in the signature to generate a description for.

    Returns:
        `str`: The description.
    
dpkd/transformers/utils/check_docstrings.py