'Flag, approve, or remove some comments from an admin action. Actually
calls the `action` argument to perform the heavy lifting.'

def _bulk_flag(self, request, queryset, action, done_message):

    n_comments = 0
    for comment in queryset:
        action(request, comment)
        n_comments += 1
    self.message_user(request, (done_message % n_comments))
