Converts an asynchronous async tree into a synchronous plain JavaScript object. The supplied argument can be any treelike object such as a JSON/YAML file, file system folder, etc. If omitted, @plain converts the current tree — in the command line, this will be the current folder — to a plain JavaScript object.
A common use for @plain is to convert a tree into a form that you can pass to any function that works with plain JavaScript objects.