docs: def find_layer(file_path):
      """Finds the layer used on the specified scheme.tl file."""
      layer_regex = re.compile(r'^//\s*LAYER\s*(\d+)$')
      with file_path.open('r') as file:
          for line in file:
              match = layer_regex.match(line)
              if match:
                  return int(match.group(1))