Owl_utils_multimap.Makeval empty : 'a tThe empty multimap.
val is_empty : 'a t -> boolCheck whether the multimap is empty.
mem k m returns true is the multimap m contains at least one binding for k, false otherwise.
add k v m returns a multimap containing the same bindings as m, plus a binding from k to v. Previous bindings for k are hidden by the new binding (they can be restored by calling remove k m).
remove k v m returns a multimap with the same bindings as m, except for the binding of k: the last value that was bound to it is removed. If there is no binding for k in m, raises `Not_found`.
find k m returns the last added binding of k in m, or raises Not_found if there is no such binding.
max_binding m returns the greatest binding in m. Raises Not_found if m is empty.