message: Add a comment why the result type of tf.ToBoolop is always ranked tensor type.
diff: @@ -2128,7 +2128,8 @@ class ToBoolOfRankedTensor : public OpRewritePattern<ToBoolOp> {
  // If the input is an unranked tensor, cannpt rewrite.
  if (!type) return failure();
  - // Expected return type of the ToBool operation.
  + // Expected return type of the ToBool operation. The return type of ToBool
  + // operation is always 0D tensor of bool type.
  auto result_type = op.getResult().getType().cast<RankedTensorType>();
  // If input is already a tensor<i1>, it can be folded into an identity.
  