code: def _norm_to_list_of_layers(maybe_layers):
      """Normalizes to a list of layers.
  
      Args:
        maybe_layers: A list of data[1] or a list of list of data.
  
      Returns:
        List of list of data.
  
      [1]: A Functional model has fields 'inbound_nodes' and 'output_layers' which can
      look like below:
      - ['in_layer_name', 0, 0]
      - [['in_layer_is_model', 1, 0], ['in_layer_is_model', 1, 1]]
      The data inside the list seems to describe [name, size, index].
      """
      return (
          maybe_layers
          if isinstance(maybe_layers[0], (list,))
          else [maybe_layers]
      )
  
file_path: tensorboard/tensorboard/plugins/graph/keras_util.py
imports: from tensorboard.compat.proto.graph_pb2 import GraphDef
  from tensorboard.compat.tensorflow_stub import dtypes
label_desc: Use image node_id 4 for calling a global function with example usage: _norm_to_list_of_layers(maybe_layers) and returns: unknown