code: private String formatPointer(PatriciaTrie.PatriciaNode<V> from, PatriciaTrie.PatriciaNode<V> to, String label,
                      String tailport) {
          StringBuilder builder = new StringBuilder();
          builder.append(getNodeId(from));
          builder.append(" -> ");
          builder.append(getNodeId(to));
          builder.append(" [ ");
          builder.append("label=\"");
          builder.append(label);
          builder.append(" \"");
          builder.append("tailport=\"");
          builder.append(tailport);
          builder.append(" \"");
          builder.append("fontcolor=\"#666666\" ");
          builder.append(" ]");
          builder.append("\n");
          return builder.toString();
      }
docs: Formats a link between two nodes
  
  @param from  from node
  @param to  to node
  @param label  label for this link
  @param tailport  tail port to use when formatting (dot-specific, "sw" or "se)
  @return formatted link, not null