我们可以向xml rpc服务器注册多少个类/实例?

I'm trying to create 2 classed in xml rpc server module and then registering the instances of the both the classes to xml rpc server. I'm able to run the methods from both the instances when registered alone , however when i run only on of them get register and the other one throws error. Also I'm only able to see the methods of class whose instance i've registered last. I was wondering is there is limation on the no. of instances i can register in server, as I remember reading something like this but I can't find mention in the documentation now? I'm trying to create 2 classed in xml rpc serve