// op into an op with a single varidic output in `.td`.
    auto converted = rewriter.create<TFL::CustomOp>(
        op->getLoc(), op->getResultTypes(), op->getOperands(),
        "TensorListPopBack", TFL::ConstBytesAttr::get(getContext(), ""));
    rewriter.replaceOp(op, converted.getResults());
    return success();
  }
};

struct ConvertTensorListPushBack

    llvm::SmallDenseMap<Value, SizeInfo>* buffer_to_size) {
  auto buffer = pop.getInputHandle();
  auto it = buffer_to_size->find(buffer);
  if (it == buffer_to_size->end()) {
    pop.emitOpError("found tf.TensorListPopBack on unknown TensorList.");
    return failure();
  }
  if (it->getSecond().fixed) {
    return pop.emitError("cannot pop on a fixed-size tensor list");
  }
  auto size = it->getSecond().size;