code: def test_pngsuite():
      files = sorted(
          (Path(__file__).parent / "baseline_images/pngsuite").glob(
              "basn*.png"
          )
      )
  
      plt.figure(figsize=(len(files), 2))
  
      for i, fname in enumerate(files):
          data = plt.imread(fname)
          cmap = None  # use default colormap
          if data.ndim == 2:
              # keep grayscale images gray
              cmap = cm.gray
          plt.imshow(data, extent=(i, i + 1, 0, 1), cmap=cmap)
  
      plt.gca().patch.set_facecolor("#ddffff")
      plt.gca().set_xlim(0, len(files))
  
file_path: matplotlib/lib/matplotlib/tests/test_png.py
imports: from io import BytesIO
  from pathlib import Path
  import pytest
  from matplotlib.testing.decorators import image_comparison
  from matplotlib import cm, pyplot
label_desc: Use image node_id 1 for calling a global function with example usage: test_pngsuite() without return types