Return the USB device's manufacturer string descriptor.

        This property will cause some USB traffic the first time it is accessed
        and cache the resulting value for future use.

def manufacturer(self):
        """ Return the USB device's manufacturer string descriptor.

        This property will cause some USB traffic the first time it is accessed
        and cache the resulting value for future use.
        """
        if self._manufacturer is None:
            self._manufacturer = util.get_string(self, self.iManufacturer)
        return self._manufacturer