Reverse features between inputs and targets if the problem is '_rev'.

def maybe_reverse_features(self, feature_map):
    """Reverse features between inputs and targets if the problem is '_rev'."""
    if not self._was_reversed:
      return
    inputs = feature_map.pop("inputs", None)
    targets = feature_map.pop("targets", None)
    inputs_seg = feature_map.pop("inputs_segmentation", None)
    targets_seg = feature_map.pop("targets_segmentation", None)
    inputs_pos = feature_map.pop("inputs_position", None)
    targets_pos = feature_map.pop("targets_position", None)
    if inputs is not None:
      feature_map["targets"] = inputs
    if targets is not None:
      feature_map["inputs"] = targets
    if inputs_seg is not None:
      feature_map["targets_segmentation"] = inputs_seg
    if targets_seg is not None:
      feature_map["inputs_segmentation"] = targets_seg
    if inputs_pos is not None:
      feature_map["targets_position"] = inputs_pos
    if targets_pos is not None:
      feature_map["inputs_position"] = targets_pos