(* Just an auxiliary one that is more convenient to use *)

Lemma sigma_table_change_aux :
only_once Site eq_site_dec s0 LS ->
(sigma_table Site LS Data f (update_table Site eq_site_dec Data t s0 d0) +
f s0 (t s0) - f s0 d0)%Z = sigma_table Site LS Data f t.