How to Impersonate User in IFS

DECLARE
   backup_user_    VARCHAR2(20);
   temp_user_      VARCHAR2(20) := 'RMAX';
BEGIN
   backup_user_ := Fnd_Session_API.Get_Fnd_User;
   
   Fnd_Session_API.Impersonate_Fnd_User(temp_user_);
   
   -- TODO: Logic
   
   Fnd_Session_API.Reset_Fnd_User;
END;