code: def on_menu_import_meas_file(self, event):
          
          # use new measurement file and corresponding WD
          meas_file = self.choose_meas_file()
          WD = os.path.split(meas_file)[0]
          self.WD = WD
          self.magic_file = meas_file
          # reset backend with new files
          self.reset_backend()
docs: Open measurement file, reset self.magic_file
          and self.WD, and reset everything.