<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def filter_products(self, desired_prods):
 """When asked for a product, filter only those on this list."""


        self.filter_prods = True
        self.desired_prods = set(desired_prods)