How to get “price_retail” field value in tempate?

I am trying access price_retail field in product detail page using template tag purchase_info_for_product. but am not getting the value of price_retail.

 {% purchase_info_for_product request product as session %}     {{ session.price.price_retail|currency:session.price.currency }} 

but i am able to access fields like incl_tax, excl_tax