public Logger delegate() {
        if (_delegate != null) {
            return _delegate;
        }
        if (createdPostInitialization) {
            return NOPLogger.NOP_LOGGER;
        } else {
            return getEventRecordingLogger();
        }
    }
Return the delegate logger instance if set. Otherwise, return a {@link NOPLogger}
instance.
slf4j-api/src/main/java/org/slf4j/helpers/SubstituteLogger.java