def get_mentions(self, message):
        """ Remove duplicates in a case-insensitive way while preserving the original order
            Return all mentions in lower case *without* their prefixes. (So return ['clyde'], not ['@clyde'])
        >>> BaseBot().get_mentions("This is a @user")
        ['user']
        >>> BaseBot().get_mentions("This is empty")
        []
        >>> BaseBot().get_mentions("title case and end of string @mention @ChangeTip. and @")
        ['mention', 'changetip']
        >>> BaseBot().get_mentions("@ This one has an empty one and two @mention-69 @changetip.")
        ['mention-69', 'changetip']
        >>> BaseBot().get_mentions("This one has a dupe @mention-69 @changetip and @mention-69.")
        ['mention-69', 'changetip']
        """
        mentions = re.findall(re.escape(self.prefix) + '([\w-]+)', message)
        mentions_set = set([m.lower() for m in mentions])

        deduped_mentions = []
        for m in mentions:
            m = m.lower()
            if m in mentions_set:
                mentions_set.remove(m)
                deduped_mentions.append(m)

        return deduped_mentions