'Return the absolute path to the directory containing this books files as a unicode string.'

def abspath(self, index, index_is_id=False, create_dirs=True):

    path = os.path.join(self.library_path, self.path(index, index_is_id=index_is_id))
    if (create_dirs and (not os.path.exists(path))):
        os.makedirs(path)
    return path
