QWeb how to add record to record set

Question

I have the following variables in Odoo QWeb:

a = sale.order(5,6,7,8,)
b = sale.order(15,)

How can I add b to a so:

a = sale.order(5,6,7,8,15,)

Answer 1

 <t t-set="a" t-value="a | b"/>

Source.