          self._stop = False
          self._save_now = False
          self._refresh_preview = False
          self._preview_buffer = dict()
          self._lock = Lock()
  
          logger.debug("Initialized %s", self.__class__.__name__)
  
 
</s>
        self._toggle_preview_mask = False
          self._stop = False
          self._save_now = False
        self._toggle_preview_mask = False
          self._refresh_preview = False
          self._preview_buffer = dict()
          self._lock = Lock()
  
          logger.debug("Initialized %s", self.__class__.__name__)
  
keep add keep keep keep keep keep keep
 - added push t to disable mask display at preview window

trsprmvd

- added extra checks for mask presence in the set
scripts/train.py