def open(self):
        """
        Open device.
        Returns an USBDeviceHandle instance.
        """
        handle = libusb1.libusb_device_handle_p()
        mayRaiseUSBError(libusb1.libusb_open(self.device_p, byref(handle)))
        result = USBDeviceHandle(self.__context, handle, self)
        self.__close_set.add(result)
        return result