message: Update labels docstring to match.
diff: @@ -151,7 +151,7 @@ class _Head(object):
  features: Input `dict` of `Tensor` objects.
  mode: Estimator's `ModeKeys`.
  logits: logits `Tensor` to be used for loss construction.
  - labels: Labels `Tensor`.
  + labels: Labels `Tensor`, or `dict` of same.
  Returns:
  A LossAndLabels that contains the `Tensor` representing the loss and
  