private static String[] defSchema(Class<? extends ConfigInstance> configClass) {
        if (configClass==null) return new String[0];
        try {
            Field f = configClass.getField("CONFIG_DEF_SCHEMA");
            return (String[]) f.get(configClass);
        } catch (NoSuchFieldException e) {
            return new String[0];
        } catch (Exception e) {
            throw new ConfigurationRuntimeException(e);
        }
    }
The def file payload of the actual class of the given config.

@param configClass the class of a generated config instance
@return a String array with the config definition (one line per element)
config/src/main/java/com/yahoo/vespa/config/protocol/DefContent.java