code: def dictlist_convert_to_string(dict_list: Iterable[Dict], key: str) -> None:
      
      for d in dict_list:
          d[key] = str(d[key])
          if d[key] == "":
              d[key] = None
docs: Process an iterable of dictionaries. For each dictionary ``d``, convert
      (in place) ``d[key]`` to a string form, ``str(d[key])``. If the result is a
      blank string, convert it to ``None``.