code: def release(self, device_info):
          
          if _debug: DeviceInfoCache._debug("release %r", device_info)
  
          # this information record might be used by more than one SSM
          if device_info._ref_count == 0:
              raise RuntimeError("reference count")
  
          # decrement the reference count
          device_info._ref_count -= 1
docs: This function is called by the segmentation state machine when it
          has finished with the device information.