2.6 Pict Finders
Locates a pict designated by find is within pict. If
find is a pict, then the pict must have been created
as some combination involving find.
If find is a list, then the first element of find
must be within pict, the second element of find must
be within the second element, and so on.
Returns #t if v is a pict or a non-empty
list of picts.
Creates a pict that has the same drawing and bounding box of
pict, but which hides all of its sub-picts so that they
cannot be found with functions like lt-find.