code: def convert_notebook(self, fname):
          
          try: 
              script = nbexporter().from_filename(fname)[0]
          except Exception as e:
              QMessageBox.critical(self, _('Conversion error'), 
                                   _("It was not possible to convert this "
                                   "notebook. The error is:\n\n") + \
                                   to_text_string(e))
              return
          self.sig_new_file.emit(script)
docs: Convert an IPython notebook to a Python script in editor