let add_in_message_stack (name_in_session : string) (state : string) (message : string) : unit =
let message_stack_name = (name_in_session,state,"_message_stack") in
if(List.mem (message_stack_name,message) (!remove_of_stack))
then remove_of_stack:=remove (message_stack_name,message) (!remove_of_stack)
else add_on_stack:= (message_stack_name,message)::(!add_on_stack);
Hashtbl.add message_stack message_stack_name message