code: def _is_png(filename: str) -> bool:
      """
      Determines if a file contains a PNG format image.
  
      Args:
      filename: string, path of the image file.
  
      Returns:
      boolean indicating if the image is a PNG.
  
      """
      # File list from:
      # https://github.com/cytsai/ilsvrc-cmyk-image-list
      return "n02105855_2933.JPEG" in filename
  
imports: from datetime import datetime
  import math
  import os
  import random
  from typing import Iterable, List, Mapping, Union, Tuple
  import sys
  import threading
  import numpy
  import tensorflow
label_desc: Use image node_id 9 for calling a global function with example usage: _is_png(filename) and returns: unknown