def get_usage_string(self):
        """Returns usage representation string (as embedded in HID device
        if available)
        """
        if self.string_index:
            usage_string_type = c_wchar * MAX_HID_STRING_LENGTH
            # 128 max string length
            abuffer = usage_string_type()
            hid_dll.HidD_GetIndexedString(
                self.hid_report.get_hid_object().hid_handle,
                self.string_index,
                byref(abuffer), MAX_HID_STRING_LENGTH-1 )
            return abuffer.value
        return ""
Returns usage representation string (as embedded in HID device
        if available)