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

    If there is only 1 argument that looks like a version, returns the argument.
    Otherwise, returns None.
    """
    if len(arguments) != 1:
        return None

    version = arguments[0]

    parts = version.split(".")
    if len(parts) != 3:
        # Not of the form: MAJOR.MINOR.PATCH
        return None

    if not all(part.isdigit() for part in parts):
        # Not all segments are integers.
        return None

    # All is good.
    return version