public static NormalizedParameters normalize(LoggingEvent event) {
        return normalize(event.getMessage(), event.getArgumentArray(), event.getThrowable());
    }
This method serves to normalize logging call invocation parameters.

More specifically, if a throwable argument is not supplied directly, it
attempts to extract it from the argument array.
slf4j-api/src/main/java/org/slf4j/helpers/NormalizedParameters.java