message: Clarify the role of replicate_model_fn.Mode better.
diff: @@ -47,7 +47,11 @@ from tensorflow.python.training import training_util
  class Mode(object):
  - """Modes for variables replication used for forcing a particular mode."""
  + """Modes for variables replication used for forcing a particular mode.
  +
  + Forcing a mode is meant for performance experimentation purposes rather than
  + for general use cases.
  + """
  AUTO = 0
  """Use internal heuristics for choosing the best Mode value.
  