code: def normalize_dataset_url_or_urls(dataset_url_or_urls):
      if isinstance(dataset_url_or_urls, list):
          if not dataset_url_or_urls:
              raise ValueError("dataset url list must be non-empty.")
          return [normalize_dir_url(url) for url in dataset_url_or_urls]
      else:
          return normalize_dir_url(dataset_url_or_urls)
  
imports: import collections.abc
  import logging
  import warnings
  import six
  from pyarrow import parquet
  from petastorm.arrow_reader_worker import ArrowReaderWorker
  from petastorm.cache import NullCache
  from petastorm.errors import NoDataAvailableError
  from petastorm.etl import dataset_metadata, rowgroup_indexing
  from petastorm.etl.dataset_metadata import PetastormMetadataError, infer_or_load_unischema
  from petastorm.fs_utils import get_filesystem_and_path_or_paths, normalize_dir_url
  from petastorm.local_disk_cache import LocalDiskCache
  from petastorm.ngram import NGram
  from petastorm.predicates import PredicateBase
  from petastorm.py_dict_reader_worker import PyDictReaderWorker
  from petastorm.reader_impl.arrow_table_serializer import ArrowTableSerializer
  from petastorm.reader_impl.pickle_serializer import PickleSerializer
  from petastorm.selectors import RowGroupSelectorBase
  from petastorm.transform import transform_schema
  from petastorm.workers_pool.dummy_pool import DummyPool
  from petastorm.workers_pool.process_pool import ProcessPool
  from petastorm.workers_pool.thread_pool import ThreadPool
  from petastorm.workers_pool.ventilator import ConcurrentVentilator
label_desc: Use image node_id 1 for calling a global function with example usage: normalize_dataset_url_or_urls(dataset_url_or_urls) and returns: unknown, normalize_dir_url