docs: def taxtable_to_tree(handle):
      """Read a CSV taxonomy from *handle* into a Tree."""
      c = csv.reader(handle, quoting=csv.QUOTE_NONNUMERIC)
      header = next(c)
      rootdict = dict(list(zip(header, next(c))))
      t = Tree(rootdict['tax_id'], rank=rootdict[
               'rank'], tax_name=rootdict['tax_name'])
      for l in c:
          d = dict(list(zip(header, l)))
          target = t.descendents[d['parent_id']]
          target(Tree(d['tax_id'], rank=d['rank'], tax_name=d['tax_name']))
      return t