Return file to browser in the backend

[evandeng2009]

Describe the bug
I like the way that no record shown in browser console when call State.functions. Right now I'm trying to provide a button for downloading files. As discussed in #909, a link should be clicked by user. Any way to directly retun the file to browser for downloading and no link shown? By the way, what's the development status of pc.download_files()?

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[Lendemor]

Solved by #1797