[slf4j-dev] Why doesn't log4j-over-slf4j have a method for Category.setLevel?

Log4j-1.2.9.jar has a Category.setLevel(org.apache.log4j.Level level) method, but log4j-over-slf4j doesn't and this is causing an AbstractMethodError when I try to use a library that uses log4j. Is there any particular reason this method wasn't implemented, or is this a bug? Thanks