def completion(self, device, folder):
return self.get(<EOL>'<STR_LIT>',<EOL>params={'<STR_LIT>': folder, '<STR_LIT>': device}<EOL>).get('<STR_LIT>', None)<EOL>
Returns the completion percentage (0 to 100) for a given device
            and folder.

            Args:
                device (str): The Syncthing device the folder is syncing to.
                folder (str): The folder that is being synced.

            Returs:
                int