'Make sure that we perform a thread safe check on the self._comments
dict, in order to avoid duplicates.'

def _is_new(self, comment, response):

    with self._plugin_lock:
        try:
            comment_data = self._comments.get(comment, None)
        except NoSuchTableException as nste:
            self._handle_no_such_table(comment, response, nste)
        response_url = response.get_url()
        if (comment_data is None):
            self._comments[comment] = [(response_url, response.id)]
            return True
        else:
            for (saved_url, response_id) in comment_data:
                if (response_url == saved_url):
                    return False
            else:
                comment_data.append((response_url, response.id))
                self._comments[comment] = comment_data
                return True
