def _readString(self, length_fmt="H"):
        """
        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
        """
        (length,) = self._readStruct(">{0}".format(length_fmt))
        ba = self.object_stream.read(length)
        return to_unicode(ba)
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