code: def compose_tree_url(tree, issn_url=False):
      
      url = compose_tree_path(tree, issn_url)
  
      if WEB_PORT == 80:
          return "%s://%s%s" % (_PROTOCOL, WEB_ADDR, url)
  
      return "%s://%s:%d%s" % (_PROTOCOL, WEB_ADDR, WEB_PORT, url)
docs: Compose full url for given `tree`, with protocol, server's address and
      port.
  
      Args:
          tree (obj): :class:`.Tree` instance.
          issn_url (bool, default False): Compose URL using ISSN.
  
      Returns:
          str: URL of the tree