code: def getTransfer(self, iso_packets=0):
          
          result = USBTransfer(
              self.__handle, iso_packets,
              self.__inflight_add, self.__inflight_remove,
          )
          self.__transfer_set.add(result)
          return result
docs: Get an USBTransfer instance for asynchronous use.
          iso_packets: the number of isochronous transfer descriptors to
            allocate.