code: def expand_mentions(text, embed_names=True):
      
      if embed_names:
          mention_format = "@<{name} {url}>"
      else:
          mention_format = "@<{url}>"
  
      def handle_mention(match):
          source = get_source_by_name(match.group(1))
          if source is None:
              return "@{0}".format(match.group(1))
          return mention_format.format(
              name=source.nick,
              url=source.url)
  
      return short_mention_re.sub(handle_mention, text)
docs: Searches the given text for mentions and expands them.
  
      For example:
      "@source.nick" will be expanded to "@<source.nick source.url>".