message: Update docstring for tpu-config
diff: @@ -36,10 +36,16 @@ class TPUConfig(
  global step is increased `iterations_per_loop` times in one `Session.run`.
  It is recommended to be set as number of global steps for next checkpoint.
  num_shards: The number of TPU shards in the system.
  - per_host_input_for_training: If `True`, `input_fn` is invoked per host
  - rather than per shard. Note: This behavior is going to be default as
  - `True` soon, so this flag will be removed after that. Also note that this
  - only works for single-host TPU training now.
  + per_host_input_for_training: If `True`, `input_fn` is invoked Per-Host
  + rather than Per-Core. With Per-Host input pipeline deployment, `input_fn`
  + is invoked once on each host. To be precise, with a global batch size
  + `train_batch_size` in `TPUEstimator` constructor, the batch size for each
  + shard is `train_batch_size` // #hosts. With Per-Core input pipeline
  + deployment, the shard batch size is `train_batch_size` // #cores. Note:
  + This behavior is going to be default as `True` soon, so this flag will be
  + removed after that. Also note that this only works for single-host TPU
  + training now (tracked in b/67051042). For multi-host, please use Per-Core,
  + i.e., `False` for `per_host_input_for_training`.
  """
  def __new__(cls,
  