+| lapply (in_comp_lift_bi f … Ht1) -Ht1 #Ht1
+| lapply (eq_lift_bi f … Ht2) -Ht2 #Ht2
+ @(subset_eq_trans … Ht2) -t2
+ @(subset_eq_trans … (lift_fsubst …))
+ [ <structure_append <structure_A_sn <structure_append <structure_L_sn
+ | //
+ | /2 width=2 by ex_intro/
+ | //
+ ]
+]
+