Need clarification on SEGW for odata service

Hi Experts,

I am traditionally creating Model provider class(MDP) & Data provider class(RDP) in se80, intergration them with model and generating the service.

But now for my new assignment i am starting on SEGW tcode where i am creating the entityset and entity as below

Now i have created the runtime airfacts which inturn creted the MDP & RDP. in traditional method we will creating the get_entity_set in /IWBEP/IF_MGW_APPL_SRV_RUNTIME~GET_ENTITYSET. but here the methods productset_get_entityset is created where i am writing the business logic, i have kept the breakpoint but it is not triggered and in the execution screen the productset_get_entityset doesn't available, then i found that this is in protected method as shown below.

My question is: where do i need to write the business logic. Please help me. Awaiting for your reply.

Thanks,

Gowtham