module PolySet:This module provides an implementation of AVL trees with a polymorphic element type. The implementation uses the standard library's polymorphicReins.Sets.PolySetSigStd
compare function internally and may not be
as efficient as the Reins.AVLSet.MonoSet module which allows the use
of a more efficient comparison function.type 'a t
type 'a cursor
type ('a, 'b) result
include Reins.Sets.Set_
val to_string : ('a -> string) -> 'a set -> string