code: private static <K, V> Set<Entry<K, Collection<V>>> constrainedAsMapEntries(
        Set<Entry<K, Collection<V>>> entries, MapConstraint<? super K, ? super V> constraint) {
      return new ConstrainedAsMapEntries<K, V>(entries, constraint);
    }
docs: Returns a constrained view of the specified set of {@code asMap} entries,
  using the specified constraint. The {@link Entry#setValue} operation will
  be verified with the constraint, and the collection returned by {@link
  Entry#getValue} will be similarly constrained. The {@code add} and {@code
  addAll} operations simply forward to the underlying set, which throws an
  {@link UnsupportedOperationException} per the multimap specification.
  
  @param entries the entries to constrain
  @param constraint the constraint for the entries
  @return a constrained view of the entries