message: Migration to python 3 for estimator.predict.
diff: @@ -3105,7 +3105,7 @@ class _SignalsHelper(object):
  def __init__(self, signals):
  self._signal_keys = []
  - for key in sorted(signals.iterkeys()):
  + for key in sorted(iter(signals.keys())):
  self._signal_keys.append(key)
  @property
  @@ -3117,7 +3117,7 @@ class _SignalsHelper(object):
  @staticmethod
  def as_tensor_list(signals):
  - return [signals[key] for key in sorted(signals.iterkeys())]
  + return [signals[key] for key in sorted(iter(signals.keys()))]
  def _verify_cross_hosts_transfer_size(tensor_dict, message):
  