(defmacro at [node-or-nodes & rules]
  `(-> ~node-or-nodes as-nodes 
     ~@(for [[s t] (partition 2 rules)]
         (if (= :lockstep s)
           `(lockstep-transform 
              ~(into {} (for [[s t] t] 
                          [(if (static-selector? s) (cacheable s) s) t])))
           `(transform ~(if (static-selector? s) (cacheable s) s) ~t)))))