code: def save_callback(operation, graphdef):
      '''callback from save thread'''
      if operation == 'test':
          for e in graphdef.expressions:
              if expression_ok(e):
                  graphdef.expression = e
                  display_graph(graphdef)
                  return
          mestate.console.writeln('Invalid graph expressions', fg='red')
          return
      if operation == 'save':
          save_graph(graphdeff save_callback(operation, graphdef):
      '''callback from save thread'''
      if operation == 'test':
          for e in graphdef.expressions:
              if expression_ok(e):
                  graphdef.expression = e
                  display_graph(graphdef)
                  return
          mestate.console.writeln('Invalid graph expressions', fg='red')
          return
      if operation == 'save':
          save_graph(graphdef)
docs: callback from save thread