public Builder level(String level) {
            level = level.toLowerCase();
            if (level.equals("info") || level.equals("debug") || level.equals("trace")) {
                this.level = level;
            } else {
                if (verbose) {
                    System.err.println("level not info/debug/trace : " + level);
                }
            }
            return this;
        }
Should LogTransformer be verbose in what it does? This currently list the
names of the classes being processed.

@param b
@return
slf4j-ext/src/main/java/org/slf4j/instrumentation/LogTransformer.java