def contains_id? id; @messages.member?(id) && !@messages[id].empty? end
def thread_for m; thread_for_id m.id end
def contains? m; contains_id? m.id end
def contains_id? id; @messages.member?(id) && !@messages[id].empty? end
def thread_for m; thread_for_id m.id end
def contains? m; contains_id? m.id end