docs: def _filter_settings(settings, prefix):
      """
      Filter all settings to only return settings that start with a certain
      prefix.
  
      :param dict settings: A settings dictionary.
      :param str prefix: A prefix.
      """
      ret = {}
      for skey in settings.keys():
          if skey.startswith(prefix):
              key = skey[len(prefix):]
              ret[key] = settings[skey]
      return ret