There is window.open_file() that can be used for opening .sublime-project files. However, it opens the file to a new tab for editing. The suggested window.open_project() would work differently. Instead of opening the file to the tab, it would act similarly if Project - Open Project... had selected from the toolbar.
def run(self, *args, **kwargs):
Служба підтримки клієнтів працює на UserEcho