docs: def setup_actions(self):
          """ Connects slots to signals """
          self.actionOpen.triggered.connect(self.on_open)
          self.actionNew.triggered.connect(self.on_new)
          self.actionSave.triggered.connect(self.on_save)
          self.actionSave_as.triggered.connect(self.on_save_as)
          self.actionQuit.triggered.connect(QtWidgets.QApplication.instance().quit)
          self.tabWidget.current_changed.connect(
              self.on_current_tab_changed)
          self.actionAbout.triggered.connect(self.on_about)