def new_list_collection(generator): return new_backend_based_collection(ListSimpleBackend(), generator)
def new_dict_collection(generator): return new_backend_based_collection(DictSimpleBackend(), generator)
def new_json_collection(directory, generator): return new_backend_based_collection(JsonSimpleBackend(directory), generator)
def new_shelve_collection(filename, generator): return new_backend_based_collection(ShelveSimpleBackend(filename), generator)