# File lib/merb-core/dispatch/session.rb, line 176
      def session(session_store = nil)
        session_store ||= default_session_store
        if class_name = self.class.registered_session_types[session_store]
          session_stores[session_store] ||= Object.full_const_get(class_name).setup(self)
        elsif fallback = self.class.registered_session_types.keys.first
          Merb.logger.warn "Session store '#{session_store}' not found. Check your configuration in init file."
          Merb.logger.warn "Falling back to #{fallback} session store."
          session(fallback)
        else
          msg = "No session store set. Set it in init file like this: c[:session_store] = 'activerecord'"
          Merb.logger.error!(msg)
          raise NoSessionContainer, msg            
        end
      end