text: import re
  import random
  import numpy as np
  import os.path
  import scipy.misc
  import shutil
  import zipfile
  import time
  import tensorflow as tf
  from glob import glob
  from urllib.request import urlretrieve
  from tqdm import tqdm
  
  
  class DLProgress(tqdm):
      last_block = 0
  
      def hook(self, block_num=1, block_size=1, total_size=None):
          self.total = total_size
          self.update((block_num - self.last_block) * block_size)
          self.last_block = block_num
  
  
  def maybe_download_pretrained_vgg(data_dir):
      """
      Download and extract pretrained vgg model if it doesn't exist
      :param data_dir: Directory to download the model to
      """
      vgg_filename = 'vgg.zip'
      vgg_path = os.path.join(data_dir, 'vgg')
      vgg_files = [
          os.path.join(vgg_path, 'variables/variables.data-00000-of-00001'),
          os.path.join(vgg_path, 'variables/variables.index'),
          os.path.join(vgg_path, 'saved_model.pb')]
  
      missing_vgg_files = [vgg_file for vgg_file in vgg_files if not os.path.exists(vgg_file)]
      if missing_vgg_files:
          # Clean vgg dir
          if os.path.exists(vgg_path):
              shutil.rmtree(vgg_path)
          os.makedirs(vgg_path)
  
          # Download vgg
          print('Downloading pre-trained vgg model...')
          with DLProgress(unit='B', unit_scale=True, miniters=1) as pbar:
              urlretrieve(
                  'https://s3-us-west-1.amazonaws.com/udacity-selfdrivingcar/vgg.zip',
                  os.path.join(vgg_path, vgg_filename),
                  pbar.hook)
  
          # Extract vgg
          print('Extracting model...')
          zip_ref = zipfile.ZipFile(os.path.join(vgg_path, vgg_filename), 'r')
          zip_ref.extractall(data_dir)
          zip_ref.close()
  
          # Remove zip file to save space
          os.remove(os.path.join(vgg_path, vgg_filename))
  
  
  def gen_batch_function(data_folder, image_shape):
      """
      Generate function to create batches of training data
      :param data_folder: Path to folder that contains all the datasets
      :param image_shape: Tuple - Shape of image
      :return:
      """
      def get_batches_fn(batch_size):
          """
          Create batches of training data
          :param batch_size: Batch Size
          :return: Batches of training data
          """
          image_paths = glob(os.path.join(data_folder, 'image_2', '*.png'))
          label_paths = {
              re.sub(r'_(lane|road)_', '_', os.path.basename(path)): path
              for path in glob(os.path.join(data_folder, 'gt_image_2', '*_road_*.png'))}
          background_color = np.array([255, 0, 0])
  
          random.shuffle(image_paths)
          for batch_i in range(0, len(image_paths), batch_size):
              images = []
              gt_images = []
              for image_file in image_paths[batch_i:batch_i+batch_size]:
                  gt_image_file = label_paths[os.path.basename(image_file)]
  
                  image = scipy.misc.imresize(scipy.misc.imread(image_file), image_shape)
                  gt_image = scipy.misc.imresize(scipy.misc.imread(gt_image_file), image_shape)
  
                  gt_bg = np.all(gt_image == background_color, axis=2)
                  gt_bg = gt_bg.reshape(*gt_bg.shape, 1)
                  gt_image = np.concatenate((gt_bg, np.invert(gt_bg)), axis=2)
  
                  images.append(image)
                  gt_images.append(gt_image)
  
              yield np.array(images), np.array(gt_images)
      return get_batches_fn
  
      
  
  def gen_test_output(sess, logits, keep_prob, image_pl, data_folder, image_shape):
      """
      Generate test output using the test images
      :param sess: TF session
      :param logits: TF Tensor for the logits
      :param keep_prob: TF Placeholder for the dropout keep robability
      :param image_pl: TF Placeholder for the image placeholder
      :param data_folder: Path to the folder that contains the datasets
      :param image_shape: Tuple - Shape of image
      :return: Output for for each test image
      """
      for image_file in glob(os.path.join(data_folder, 'image_2', '*.png')):
          image = scipy.misc.imresize(scipy.misc.imread(image_file), image_shape)
  
          im_softmax = sess.run(
              [tf.nn.softmax(logits)],
              {keep_prob: 1.0, image_pl: [image]})
          im_softmax = im_softmax[0][:, 1].reshape(image_shape[0], image_shape[1])
          segmentation = (im_softmax > 0.5).reshape(image_shape[0], image_shape[1], 1)
          mask = np.dot(segmentation, np.array([[0, 255, 0, 127]]))
          mask = scipy.misc.toimage(mask, mode="RGBA")
          street_im = scipy.misc.toimage(image)
          street_im.paste(mask, box=None, mask=mask)
  
          yield os.path.basename(image_file), np.array(street_im)
  
  
  def save_inference_samples(runs_dir, data_dir, sess, image_shape, logits, keep_prob, input_image):
      # Make folder for current run
      output_dir = os.path.join(runs_dir, str(time.time()))
      if os.path.exists(output_dir):
          shutil.rmtree(output_dir)
      os.makedirs(output_dir)
  
      # Run NN on test images and save them to HD
      print('Training Finished. Saving test images to: {}'.format(output_dir))
      image_outputs = gen_test_output(
          sess, logits, keep_prob, input_image, os.path.join(data_dir, 'data_road/testing'), image_shape)
      for name, image in image_outputs:
          scipy.misc.imsave(os.path.join(output_dir, name), image)
          
          
          
  
  
  