calls +qeu treap-order validation in mold with $|
$| (tree (pair key value))
|=(a=(tree (pair)) ~(apt by a))
::
-+* qeu [item] (tree item) :: queue
++* qeu [item] :: queue
+ $| (tree item)
+ |=(a=(tree) ~(apt to a))
::
+* set [item] :: set
$| (tree item)
