import tensorflow as tf

  """Download the data from source url, unless it's already here.

  Args:
    filename: string, name of the file in the directory.
    work_directory: string, path to working directory.
    source_url: url to download from if file doesn't exist.

  Returns:
    Path to resulting file.
  """
  if not tf.gfile.Exists(work_directory):
    tf.gfile.MakeDirs(work_directory)
  filepath = os.path.join(work_directory, filename)
  if not tf.gfile.Exists(filepath):
    temp_file_name, _ = urllib.request.urlretrieve(source_url)
    tf.gfile.Copy(temp_file_name, filepath)
    with tf.gfile.GFile(filepath) as f:
      size = f.size()
      print("Successfully downloaded", filename, size, "bytes.")
  return filepath


def load_dataset(data_dir, url, batch_size):
  """Loads the colors data at path into a PaddedDataset."""

  # Downloads data at url into data_dir/basename(url). The dataset has a header
