code: def maybe_download_image_dataset(image_ids, target_dir):
    
  
    tf.gfile.MakeDirs(target_dir)
  
    num_images = len(image_ids)
  
    for i, image_id in enumerate(image_ids):
  
      destination = os.path.join(target_dir, "%s.jpg" % i)
      tmp_destination = "%s.temp" % destination
  
      source_url = ("http://api.brain-map.org/api/v2/"
                    "section_image_download/%s" % image_id)
  
      if tf.gfile.Exists(destination):
        tf.logging.info("Image with ID already present, "
                        "skipping download (%s of %s)." % (
                            i+1, num_images
                        ))
        continue
  
      tf.logging.info("Downloading image with id %s (%s of %s)" % (
          image_id, i+1, num_images
      ))
  
      response = requests.get(source_url, stream=True)
  
      response.raise_for_status()
  
      with tf.gfile.Open(tmp_destination, "w") as f:
        for block in response.iter_content(1024):
          f.write(block)
  
      tf.gfile.Rename(tmp_destination, destination)
docs: Download a set of images from api.brain-map.org to `target_dir`.
  
    Args:
      image_ids: list, a list of image ids.
      target_dir: str, a directory to which to download the images.