code: public static List<OpensDirective>
              opensIn(Iterable<? extends Directive> directives) {
          return listFilter(directives, DirectiveKind.OPENS, OpensDirective.class);
      }
docs: Returns a list of {@code opens} directives in {@code directives}.
  @return a list of {@code opens} directives in {@code directives}
  @param directives the directives to filter
  @since 9