11.3.4 Transform-grove-spec
An object of type transform-grove-spec represents a grove to be transformed in addition to the current grove.
(transform-grove-spec? obj)
Returns #t if obj is of type transform-grove-spec, and otherwise returns #f.
(transform-grove snl obj )
snl shall be the root of a grove.  transform-grove creates a new grove from snl by adding a transform-args property to the grove root whose value is a list containing obj, , and returns an object of type transform-grove-spec specifying the transformation of that new grove.
(select-grove nl obj)
Returns a node-list containing those members of nl whose grove root has a transform-args property that contains a member equal to obj.