def _get_version_from_arguments(arguments):
    """Checks the arguments passed to `nox -s release`.

    Only 1 argument that looks like a version? Return the argument.
    Otherwise, raise a ValueError describing what's wrong.
    """
    if len(arguments) != 1:
        raise ValueError("Expected exactly 1 argument")

    version = arguments[0]
    parts = version.split(".")

    if len(parts) != 2:
        # Not of the form: YY.N
        raise ValueError("not of the form: YY.N")

    if not all(part.isdigit() for part in parts):
        # Not all segments are integers.
        raise ValueError("non-integer segments")

    # All is good.
    return version