Now that we have learned to make that small change, let's look a little closer at how Odoo is able to use the exact same template for both the quotation and the sales order. In fact you may have already figured out how Odoo does this from looking a little bit around the code we just modified.
One of the best things you can do to learn how to modify reports is looking at existing reports within Odoo and seeing how they accomplish what you may wish to accomplish. When trying to solve a problem, see if you can find another report in Odoo that is already doing something similar to what you want.