(all) => {
  /*
  list is all the files in current directory.
  allfiles: ending with `.md` and not starting with `_`.
  pubfiles: the subset containing the string `_pub`.
  files selects either of these depending on the argument passed to this file.
  */
  (list): ..
  allfiles: Tree.filter(list,
    (val, key) => key.endsWith('.md') && !key.startsWith('_'))
  pubfiles: Tree.filter(allfiles,
    (val, key) => key.includes('_pub'))

}