    # File lib/merb-core/dispatch/session.rb, line 190
          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