docs: def find_file(path, filename, max_depth=5):
    """Returns full filepath if the file is in path or a subdirectory."""
    for root, dirs, files in os.walk(path):
      if filename in files:
        return os.path.join(root, filename)
  
      # Don't search past max_depth
      depth = root[len(path) + 1:].count(os.sep)
      if depth > max_depth:
        del dirs[:]  # Clear dirs
    return None