code: def closing_plugin(self, cancelable=False):
          
          if self.busy:
              answer = QMessageBox.question(
                  self,
                  'Conda Manager',
                  'Conda Manager is still busy.\n\nDo you want to quit?',
                  buttons=QMessageBox.Yes | QMessageBox.No)
  
              if answer == QMessageBox.Yes:
                  return True
              else:
                  return False
          else:
              return True
docs: Perform actions before parent main window is closed.