private void validateField(String field, String line, int lineNum) {
        if (field.length() == 0) {
            throw new ConfigurationRuntimeException("Error on line " + lineNum + ": " + line + "\n" +
                                                    "'" + field + "' is not a valid field name");
        }
    }
Deserializes a config payload to slime

@param lines a list with config payload strings
@return an instance of the config class
config/src/main/java/com/yahoo/config/subscription/CfgConfigPayloadBuilder.java