Not able to call set_accept_focus(bool) member function

["SaiKamesh Rathinasabapathy" <rsaikamesh gmail com>]

Murray said: For now, you can probably just do
                     gtk_window_set_accept_focus(window->gobj(), true/false).

I tried using this method. But the compiler says: 'gtk_window_set_accept_focus' was not declared in this scope.

Can anyone answer me why this does not work?