def save(self, doc):
        if doc.id:
            return self.update(doc)
        else:
            return self.insert(doc)
def usage_iter(root):
    root = os.path.abspath(root)
    root_size = get_folder_size(root)
    root_string = "{0}\n{1}".format(root, root_size)
    yield [root_string, None, root_size]