code: def _load_image(filename, fmt):
      if fmt == "png":
          return find_open_image_png_function()(filename)
  
      raise NotImplementedError(
          f"Image format {fmt} not implemented yet"
      )
  
file_path: python-igraph/tests/drawing/cairo/utils.py
imports: from pathlib import Path
  import sys
  import inspect
  import functools
  from igraph.drawing import find_cairo
label_desc: Use image node_id 4 for calling a global function with example usage: _load_image(filename, fmt) and returns: find_open_image_png_function