def craw_(dir_, nest_level=0, files=None):
    dir_ = dir_['contents']

    for item in dir_:
        if not item['isfolder']:
            files.select_items([item['name'], False])

    for item in dir_:
        if item['isfolder']:
            files.tap_item([item['name'], True])
            craw_(item, nest_level+1, driver=driver, files=files)
            nest_level = 0

    for _ in range(0, nest_level):
        files.back()
        nest_level -= 1