Double checkbar environment, be remember you are bartender different the chef, you have to face the guest so you have to show best to guest.
清洁吧台内部环境记住做为一名调酒师与厨师不同的是，你要面对客人，所以你要把你最好的一面展示给客人。
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While a thread is running, either uploading or downloading, you can query it to check on its status to provide the user with feedback (e.g. a progress bar).