code: def test_valid_png(m_png):
      png = m_png._repr_png_()
      img = PIL.Image.open(io.BytesIO(png))
      assert isinstance(img, PIL.PngImagePlugin.PngImageFile)
  
file_path: folium/tests/test_repr.py
imports: import io
  import PIL.Image
  import pytest
  import folium
label_desc: Use image node_id 7 for calling a global function with example usage: test_valid_png(m_png) without return types