docs: def make_vbox_dirs(max_vbox_id, output_dir, topology_name):
      """
      Create VirtualBox working directories if required
  
      :param int max_vbox_id: Number of directories to create
      :param str output_dir: Output directory
      :param str topology_name: Topology name
      """
      if max_vbox_id is not None:
          for i in range(1, max_vbox_id + 1):
              vbox_dir = os.path.join(output_dir, topology_name + '-files',
                                      'vbox', 'vm-%s' % i)
              os.makedirs(vbox_dir)