public void visitPackageDeclaration(PackageDeclaration d) {
        d.accept(pre);

        for(ClassDeclaration classDecl: d.getClasses()) {
            classDecl.accept(this);
        }

        for(InterfaceDeclaration interfaceDecl: d.getInterfaces()) {
            interfaceDecl.accept(this);
        }

        d.accept(post);
    }