Can not automatically check whether the module is imported, alt+enter does not work properly

After I updated pycharm to 2019.2, it was not possible to automatically check whether the module was imported or not, and alt+enter could not work properly. How can I solve it?

Like the code written in the figure, "requests" is an imported third-party library, "requests" should have warning wavy line hints, but no, after "requests" press alt+enter, nothing happens.