code: public ServerBuilder addProductExtension(String name, Properties props) {
          if ((name != null) && (props != null)) {
              if (productExtensions == null) {
                  productExtensions = new HashMap<String, Properties>();
              }
              this.productExtensions.put(name, props);
          }
          return this;
      }
docs: Add a product extension.
  
  <p>
  The addProductExtension method can be called
  multiple times to add multiple extensions.
  <p>
  When the server is started, any product extension files added by this method
  will be combined with the product extension files found in other source locations.
  Any duplicate product names will invoke the following override logic: product extensions
  defined through this SPI will override product extensions defined by the Environment
  variable <code>WLP_PRODUCT_EXT_DIR</code> which in turn would override product extensions
  found in
  <code>$WLP_INSTALL_DIR/etc/extensions</code> to constitute the full set of product
  extensions for this instance of the running server.
  
  @param name The name of the product extension.
  @param props A properties file containing com.ibm.websphere.productId and com.ibm.websphere.productInstall.
  @return a reference to this object.