code: def uri_unsplit_tree(uri_tree):
      
      scheme, authority, path, query, fragment = uri_tree
      if authority:
          user, passwd, host, port = authority
          if user and passwd:
              userinfo = user + ':' + passwd
          elif user:
              userinfo = user
          elif passwd:
              userinfo = ':' + passwd
          else:
              userinfo = None
          if host and port:
              hostport = host + ':' + port
          elif host:
              hostport = host
          elif port:
              hostport = ':' + port
          else:
              hostport = None
          if userinfo and hostport:
              authority = userinfo + '@' + hostport
          elif userinfo:
              authority = userinfo + '@'
          elif hostport:
              authority = hostport
          else:
              authority = None
      if query:
          query = unsplit_query(query)
      uri = ''
      if scheme:
          uri += scheme + ':'
      if authority:
          uri += '//' + authority
      if path:
          if (not authority) and path[0:2] == '//':
              uri += '//'
          uri += path
      if query:
          uri += '?' + query
      if fragment:
          uri += '#' + fragment
      return uri
docs: Unsplit a coded URI tree, which must also be coalesced by
      uri_tree_normalize().