data Prod:
   value: string

service OpHa("op"):
    array(a: string, b: string) -> []string
    identity(a: string) -> string

func doSmth(arg: Prod) -> []string:
    v = arg.value
    a <- OpHa.identity(v)
    b = "hello"
    res <- OpHa.array(a, b)
    <- res