message: Improve documentation for CollectiveCommunication.
diff: @@ -949,11 +949,12 @@ class CollectiveCommunication(enum.Enum):
  * `RING`: TensorFlow's ring algorithms for all-reduce and
  all-gather.
  * `NCCL`: Use ncclAllReduce for all-reduce, and ring algorithms for
  - all-gather. TODO(ayushd): add ncclAllGather implementation.
  + all-gather.
  """
  AUTO = "AUTO"
  RING = "RING"
  NCCL = "NCCL"
  + # TODO(ayushd): add ncclAllGather implementation.
  # TODO(yuefengz): support in-graph collective all-reduce.
  