code: def test_format_inference_stream():
      # There's no way to infer the format, so it should default to png
      fstream = io.BytesIO(b"")
      img = Image.from_file(fstream)
  
      assert img.format == "png"
  
imports: import io
  import os
  from ipywidgets import Image
  import hashlib
  import pkgutil
  import tempfile
  from contextlib import contextmanager
label_desc: Use image node_id 13 for calling a global function with example usage: test_format_inference_stream() without return types