message: Restrict contrast_factor as scalar for AdjustContrastv2 shape
  The contrast_factor should be scalar for AdjustContrastv2.
  This fix adds the scalar restriction in the shape function.
diff: @@ -357,6 +357,9 @@ REGISTER_OP("AdjustContrastv2")
  .Input("contrast_factor: float")
  .Output("output: float")
  .SetShapeFn([](InferenceContext* c) {
  + // The contrast_factor should be scalar only.
  + ShapeHandle unused;
  + TF_RETURN_IF_ERROR(c->WithRank(c->input(1), 0, &unused));
  return shape_inference::UnchangedShapeWithRankAtLeast(c, 3);
  });
  