docs: def _decoderFromString(cfg):
          """
          Return a decoder function.
          If cfg is a string such as 'latin-1' or u'latin-1',
          then we return a new lambda, s.decode().
          If cfg is already a lambda or function, then we return that.
          """
          if isinstance(cfg, (bytes, str)):
              return lambda s: s.decode(cfg, 'replace')
          return cfg