          self._display_dims = (1, 1)
          self._tk_vars = tk_vars
          self._padding = padding
  
          self._faces = dict()
          self._centering = None
          self._faces_source = None
          self._faces_dest = None
          self._tk_image = None
  
 
</s> remove         self.source = list()  # Source images, filenames + detected faces
 </s> add         self.source = []  # Source images, filenames + detected faces </s> remove         self._tk_vars = dict()
 </s> add         self._tk_vars = {} </s> remove         defaults = {opt: self._format_to_display(d_locals["selected_{}".format(opt)])
 </s> add         defaults = {opt: self._format_to_display(d_locals[f"selected_{opt}"]) </s> remove         self._faces = dict()
 </s> add         self._faces = {} </s> remove                     new_opt = options.value  # Keep saved item for other sections
 </s> add                     # retain saved values that have not been updated
                    new_opt = self._config.get(config_section, item)
        self._faces = {}
          self._display_dims = (1, 1)
          self._tk_vars = tk_vars
          self._padding = padding
  
        self._faces = {}
          self._centering = None
          self._faces_source = None
          self._faces_dest = None
          self._tk_image = None
  
keep keep keep keep replace keep keep keep keep keep
 bugfix: Preview Tool, ensure all config items are written 
tools/preview/preview.py