default values for action parameters from function in the behavior of RAP in Odata v4

[amo_ry]

I made an action with parameters 

and i want to put default values in this parameter , so i created a function GetDefaultsForGET_SERIAL

i am trying to default it in the action like this : 

but it is not supported in my release . 

so i am trying to add it in the annotation file : 

it works with ODATA V2 with these annotations : 

but i am trying in ODATA V4 but not working: 

can any one help ?