code: public DocumentSource createDocumentSource(URL base, String urlstring)
      {
          try
          {
              Constructor<? extends DocumentSource> constr = getDocumentSourceClass().getConstructor(URL.class, String.class);
              return constr.newInstance(base, urlstring);
          } catch (Exception e) {
              log.warn("Could not create the DocumentSource instance: " + e.getMessage());
              return null;
          }
      }
docs: Creates a new instance of the {@link org.fit.cssbox.io.DocumentSource} class registered in the browser configuration.
  @param base the base URL
  @param urlstring the URL suffix
  @return the document source.