code: def __initialize_ui(self):
          
  
          self.__margin_area_LinesNumbers_widget = LinesNumbers_QWidget(self)
  
          self.__set_extra_selections()
  
          self.__set_language_description()
  
          # Signals / Slots.
          self.blockCountChanged.connect(self.__margin_area_LinesNumbers_widget.set_editor_viewport_margins)
          self.updateRequest.connect(self.__margin_area_LinesNumbers_widget.update_rectangle)
          self.cursorPositionChanged.connect(self.__set_extra_selections)
docs: Initializes the Widget ui.