code: public ServerMethodDefinition<ReqT, RespT> withServerCallHandler(
        ServerCallHandler<ReqT, RespT> handler) {
      return new ServerMethodDefinition<>(method, handler);
    }
docs: Create a new method definition with a different call handler.
  
  @param handler to bind to a cloned instance of this.
  @return a cloned instance of this with the new handler bound.