I have created BlackVarianceSurface and enabled extrapolation but unable to change extrapolation type used. It is giving flat extrapolation. Used setInterpolation to change method type but extrapolation still coming out as flat. How can that be modified?
Code is:
black_var_surface = ql.BlackVarianceSurface(calculation_date, calendar, expiration_dates, strikes, implied_vols, day_count)
black_var_surface.setInterpolation("bicubic")
black_var_surface.enableExtrapolation()