docs: def get_case_insensitive_dict_key(d: Dict, k: str) -> Optional[str]:
      """
      Within the dictionary ``d``, find a key that matches (in case-insensitive
      fashion) the key ``k``, and return it (or ``None`` if there isn't one).
      """
      for key in d.keys():
          if k.lower() == key.lower():
              return key
      return None