code: def test_png(h, f):
      if h.startswith(b"\211PNG\r\n\032\n"):
          return "png"
  
file_path: catboost/contrib/tools/python3/src/Lib/imghdr.py
imports: from os import PathLike
  import warnings
label_desc: Use image node_id 3 for calling a global function with example usage: test_png(h, f) and returns: str