These were the flags in my mind:-
--xla [XLA]           Whether to activate the XLA compilation or not
--tpu_name TPU_NAME   Name of TPU
--tpu_zone TPU_ZONE   Zone of TPU
--tpu_num_cores TPU_NUM_CORES
                        TPU: Number of TPU cores (automatically passed by
                        launcher script)

which indicates TPU/XLA is being used.
I don’t think I am ready to open PR’s yet  though I am happy to assist in other ways