class CommunitySetExprEvaluator implements CommunitySetExprVisitor<CommunitySet, CommunityContext> {

  @Override
  public @Nonnull CommunitySet visitCommunitySetExprReference(
      CommunitySetExprReference communitySetExprReference, CommunityContext arg) {
    CommunitySetExpr communitySetExpr =
        arg.getCommunitySetExprs().get(communitySetExprReference.getName());
    // conversion to VI should guarantee communitySetExpr is not null
    assert communitySetExpr != null;
    return communitySetExpr.accept(this, arg);
  }

  private  CommunitySetExprEvaluator();

}