How to have separate log4j config for library jar

We are developing client library which will be distributed as jar to other user application who will in turn create runnable application. The problem is we want to setup log4j separately for this jar so that issues can be logged correctly. As this is library we can not assume user will always use log4j they might use some other logging framework or may not initialize log4j as we want. In short we want to configure log4j separately for our library jar. Please suggest way to do this.