code: def _readString(self, length_fmt="H"):
          
          (length,) = self._readStruct(">{0}".format(length_fmt))
          ba = self.object_stream.read(length)
          return to_unicode(ba)
docs: Reads a serialized string
  
          :param length_fmt: Structure format of the string length (H or Q)
          :return: The deserialized string
          :raise RuntimeError: Unexpected end of stream