code: public void fatal(Object message, Throwable t) {
          differentiatedLog(FATAL_MARKER, CATEGORY_FQCN, LocationAwareLogger.ERROR_INT, message, t);
      }
docs: Delegates to {@link org.slf4j.Logger#error(String,Throwable)} method in
  SLF4J. In addition, the call is marked with a marker named "FATAL".