code: def get_mentions(self, message):
          
          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
docs: 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']