docs: def contextMenuEvent(self, event):
          """
          Add menu action:
          * 'Show line numbers'
          * 'Save to file'
          """
          menu = QtWidgets.QPlainTextEdit.createStandardContextMenu(self)
          mg = self.getGlobalsMenu()
  
          a0 = menu.actions()[0]
          menu.insertMenu(a0, mg)
          menu.insertSeparator(a0)
  
          menu.addSeparator()
          a = QtWidgets.QAction('Show line numbers', menu)
          l = self.codeEditor.lineNumbers
          a.setCheckable(True)
          a.setChecked(l.isVisible())
          a.triggered.connect(lambda checked: l.show() if checked else l.hide())
          menu.addAction(a)
  
          menu.addSeparator()
          a = QtWidgets.QAction('Save to file', menu)
          a.triggered.connect(self.saveToFile)
          menu.addAction(a)
  
          menu.exec_(event.globalPos())