code: def compose_tree_path(tree, issn=False):
      
      if issn:
          return join(
              "/",
              ISSN_DOWNLOAD_KEY,
              basename(tree.issn)
          )
  
      return join(
          "/",
          PATH_DOWNLOAD_KEY,
          quote_plus(tree.path).replace("%2F", "/"),
      )
docs: Compose absolute path for given `tree`.
  
      Args:
          pub (obj): :class:`.Tree` instance.
          issn (bool, default False): Compose URL using ISSN.
  
      Returns:
          str: Absolute path of the tree, without server's address and protocol.