fetch

# File actionpack/lib/action_dispatch/request/session.rb, line 133
      def fetch(key, default=Unspecified, &block)
        load_for_read!
        if default == Unspecified
          @delegate.fetch(key.to_s, &block)
        else
          @delegate.fetch(key.to_s, default, &block)
        end
      end