// CHECK-NOT: Optional
  %0 = builtin.unrealized_conversion_cast to tensor<5xi1>
  %1 = "tf.OptionalNone"() : () -> tensor<!tf_type.variant<tensor<f32>>>
  %2 = "tf.If"(%0, %1) <{else_branch = @false, is_stateless = false, then_branch = @true}>
      : (tensor<5xi1>, tensor<!tf_type.variant<tensor<f32>>>) -> (tensor<!tf_type.variant<tensor<f32>>>)
  return
}

    auto original_point = rewriter.saveInsertionPoint();
    rewriter.setInsertionPointAfter(op->getParentOfType<func::FuncOp>());
    SymbolTable manager(op->getParentOfType<ModuleOp>());

    // Constructs `then_branch`, which is executed when `if_cond` evaluates to
    // true.
    auto then_branch_op =
        rewriter.create<func::FuncOp>(loc, "cond_true", func_type);

    `tf.IfRegion` and `tf.While` is transformed to `tf.WhileRegion`.

    For example, this functional operation

    ```mlir
      %0 = "tf.If"(%arg0, %arg1) {
        then_branch = @then_branch_func, else_branch = @else_branch_func, is_stateless = false
      } : (tensor<i1>, tensor<*xf32>) -> tensor<*xf32>
    ```

    will be transformed into this region-based operation