code: def check_or_download_dataset(self):
      if not osp.exists(self.dataset_dir):
          download_dataset("dataset", dataset="culane")
          # extract .tar files in self.dataset_dir
          for fname in os.listdir(self.dataset_dir):
              logger.info("Decompressing {}...".format(fname))
              # ignore .* files
              if fname.startswith("."):
                  continue
              if fname.find(".tar.gz") >= 0:
                  with tarfile.open(
                      osp.join(self.dataset_dir, fname)
                  ) as tf:
                      tf.extractall(path=self.dataset_dir)
      logger.info("Dataset files are ready.")
  
imports: from ppdet.core.workspace import register, serializable
  import cv2
  import os
  import tarfile
  import numpy
  import os.path
  from ppdet.data.source.dataset import DetDataset
  from imgaug.augmentables.lines import LineStringsOnImage
  from imgaug.augmentables.segmaps import SegmentationMapsOnImage
  from ppdet.data.culane_utils import lane_to_linestrings
  import pickle
  from ppdet.utils.logger import setup_logger
  from .dataset import DetDataset, _make_dataset, _is_valid_file
  from ppdet.utils.download import download_dataset
label_desc: Use image node_id 3 for calling the CULaneDataSet obj's underlying member method code with example usage: obj.check_or_download_dataset() without return types