code: def maybe_download(directory, filename, uri):
    
    tf.gfile.MakeDirs(directory)
    filepath = os.path.join(directory, filename)
    if tf.gfile.Exists(filepath):
      tf.logging.info("Not downloading, file already found: %s" % filepath)
      return filepath
  
    tf.logging.info("Downloading %s to %s" % (uri, filepath))
    try:
      tf.gfile.Copy(uri, filepath)
    except tf.errors.UnimplementedError:
      if uri.startswith("http"):
        inprogress_filepath = filepath + ".incomplete"
        inprogress_filepath, _ = urllib.urlretrieve(
            uri, inprogress_filepath, reporthook=download_report_hook)
        # Print newline to clear the carriage return from the download progress
        print()
        tf.gfile.Rename(inprogress_filepath, filepath)
      else:
        raise ValueError("Unrecognized URI: " + filepath)
    statinfo = os.stat(filepath)
    tf.logging.info("Successfully downloaded %s, %s bytes." %
                    (filename, statinfo.st_size))
    return filepath
docs: Download filename from uri unless it's already in directory.
  
    Copies a remote file to local if that local file does not already exist.  If
    the local file pre-exists this function call, it does not check that the local
    file is a copy of the remote.
  
    Remote filenames can be filepaths, any URI readable by tensorflow.gfile, or a
    URL.
  
    Args:
      directory: path to the directory that will be used.
      filename: name of the file to download to (do nothing if it already exists).
      uri: URI to copy (or download) from.
  
    Returns:
      The path to the downloaded file.