code: def join_pretty_tensors(tensors, output, join_function=None, name='join'):
    
    if not tensors:
      raise ValueError('pretty_tensors must be a non-empty sequence.')
    with output.g.name_scope(name):
      if join_function is None:
        # Use depth concat
        last_dim = len(tensors[0].shape) - 1
        return output.with_tensor(tf.concat(tensors, last_dim))
      else:
        return output.with_tensor(join_function(tensors))
docs: Joins the list of pretty_tensors and sets head of output_pretty_tensor.
  
    Args:
      tensors: A sequence of Layers or SequentialLayerBuilders to join.
      output: A pretty_tensor to set the head with the result.
      join_function: A function to join the tensors, defaults to concat on the
        last dimension.
      name: A name that is used for the name_scope
    Returns:
      The result of calling with_tensor on output
    Raises:
      ValueError: if pretty_tensors is None or empty.