code: public NodeTypes getNodeTypes() {
          String url = jsonRestClient.appendToURL(ITEMS_METHOD, NODE_TYPES_SEGMENT);
          JSONRestClient.Response response = jsonRestClient.doGet(url);
          if (!response.isOK()) {
              throw new RuntimeException(JdbcI18n.invalidServerResponse.text(url, response.asString()));
          }
          return new NodeTypes(response.json());
      }
docs: Returns all the node types that are available in the repository from {@code repoUrl}
  
  @return a {@link NodeTypes} instance; never {@code null}