def download_file(url, dest=None, chunk_size=1024, replace="ask",
                  label="Downloading {dest_basename} ({size:.2f}MB)",
                  expected_extension=None):
    """Download a file from a given URL and display progress.

    :param dest: If the destination exists and is a directory, the filename
        will be guessed from the Content-Disposition header. If the destination
        is an existing file, the user will either be prompted to overwrite, or
        the file will be replaced (depending on the value of **replace**). If
        the destination does not exist, it will be used as the filename.
    :param int chunk_size: bytes read in at a time.
    :param replace: If `False`, an existing destination file will not be
        overwritten.
    :param label: a string which is formatted and displayed as the progress bar
        label. Variables provided include *dest_basename*, *dest*, and *size*.
    :param expected_extension: if set, the filename will be sanitized to ensure
        it has the given extension. The extension should not start with a dot
        (`.`).
    """
    dest = Path(dest or url.split("/")[-1])
    response = get(url, stream=True)
    if (dest.exists()
            and dest.is_dir()
            and "Content-Disposition" in response.headers):
        content_disposition = rfc6266.parse_requests_response(response)
        if expected_extension is not None:
            filename = content_disposition.filename_sanitized(
                expected_extension)
        filename = secure_filename(filename)
        dest = dest / filename
    if dest.exists() and not dest.is_dir():
        if (replace is False
                or replace == "ask"
                and not click.confirm("Replace {}?".format(dest))):
            return str(dest)
    size = int(response.headers.get("content-length", 0))
    label = label.format(dest=dest, dest_basename=dest.name,
                         size=size/1024.0/1024)
    with click.open_file(str(dest), "wb") as f:
        content_iter = response.iter_content(chunk_size=chunk_size)
        with click.progressbar(content_iter, length=size/1024,
                               label=label) as bar:
            for chunk in bar:
                if chunk:
                    f.write(chunk)
                    f.flush()
    return str(dest)
def run_model(prior, images, model, disc_reg_weight):
  """Run the model with new data and samples.

  Args:
    prior: the noise source as the generator input.
    images: images sampled from dataset.
    model: a GAN model defined in gan.py.
    disc_reg_weight: regularisation weight for discrmininator gradients.

  Returns:
    debug_ops: statistics from the model, see gan.py for more detials.
    disc_grads: discriminator gradients.
    gen_grads: generator gradients.
  """
  generator_inputs = prior.sample(FLAGS.batch_size)
  model_output = model.connect(images, generator_inputs)
  optimization_components = model_output.optimization_components

  disc_grads = tf.gradients(
      optimization_components['disc'].loss,
      optimization_components['disc'].vars)

  gen_grads = tf.gradients(
      optimization_components['gen'].loss,
      optimization_components['gen'].vars)

  if disc_reg_weight > 0.0:
    reg_grads = _compute_reg_grads(gen_grads,
                                   optimization_components['disc'].vars)
    disc_grads = _acc_grads(disc_grads, disc_reg_weight, reg_grads)

  debug_ops = model_output.debug_ops

  return debug_ops, disc_grads, gen_grads