docs: def style_checkboxes(widget):
      """
      Iterates over widget children to change checkboxes stylesheet.
  
      The default rendering of checkboxes does not allow to tell a focused one
      from an unfocused one.
      """
  
      ww = widget.findChildren(QCheckBox)
      for w in ww:
          w.setStyleSheet("QCheckBox:focus {border: 1px solid #000000;}")