private static void validateArgValue(String argStringParam) {
        String[] argStringParts = argStringParam.split("\\s+");
        if (argStringParts.length > 1) {
            throw new IllegalArgumentException("Dockerfile parse error: ARG requires exactly one argument. Provided : " + argStringParam);
        }
    }
Helper method for extractArgs(exposed for test)

@param argLines list of string arrays containing lines with words
@return map of parsed arguments
src/main/java/io/fabric8/maven/docker/util/DockerFileUtil.java