def tf_left_split(op):
  """Split the parameters of op for left recursion.

  Args:
    op: tf.Operation

  Returns:
    A tuple of the leftmost input tensor and a list of the
    remaining arguments.
  """

  if len(op.inputs) < 1:
    return None, []
  if op.type == "Concat":
    return op.inputs[1], op.inputs[2:]
  return op.inputs[0], op.inputs[1:]