Denotes a tensor as a final output of the computation.

    Args:
      tensor_name: a string, name of a tensor in the graph.

def set_tensor_final(self, tensor_name):
    """Denotes a tensor as a final output of the computation.

    Args:
      tensor_name: a string, name of a tensor in the graph.
    """
    tensor = self._name_to_tensor(tensor_name)
    self._final_tensors.add(tensor)