code: public Node nodeBy(final NetworkAddress hostname) {
          if (hostname == null) {
              return null;
          }
  
          for (Node node : nodes) {
              if (node.hostname().equals(hostname)) {
                  return node;
              }
          }
          return null;
      }
docs: Returns the node by its hostname.
  
  @param hostname the hostname of the node.
  @return the node or null if no hostname for that ip address.