message: close device in clear_session
diff: @@ -526,6 +526,8 @@ def clear_session():
  global _in_train_phase, _ctx, _dev, PLAIDML_EVENTLOG_FILENAME
  _in_train_phase = None
  _ctx = plaidml.Context()
  + if _dev:
  + _dev.close()
  _dev = None
  if PLAIDML_EVENTLOG_FILENAME:
  _ctx.set_eventlog_filename(PLAIDML_EVENTLOG_FILENAME)
  