code: protected Transformer createXmlTransformer(int numberOfBlanksToIndent) throws TransformerConfigurationException {
          TransformerFactoryConfigurer.Builder b = TransformerFactoryConfigurer.builder()
              .withExternalStylesheetLoadingDisabled()
              .withDTDLoadingDisabled();
  
          if (numberOfBlanksToIndent >= 0) {
              // not all TransformerFactories support this feature
              b = b.withSafeAttribute("indent-number", numberOfBlanksToIndent);
          }
          final TransformerFactory factory = b.build().configure(TransformerFactory.newInstance());
          final Transformer transformer = factory.newTransformer();
          transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
          transformer.setOutputProperty(OutputKeys.METHOD, "xml");
          if (numberOfBlanksToIndent >= 0) {
              try {
                  transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", String
                      .valueOf(numberOfBlanksToIndent));
              } catch (final IllegalArgumentException ex) {
                  // Could not set property '{http://xml.apache.org/xslt}indent-amount' on
                  // transformer.getClass().getName()
                  // which is fine for us
              }
              transformer.setOutputProperty(OutputKeys.INDENT, "yes");
          }
          return transformer;
      }
docs: Create a default Transformer to format a XML-Node to a String.
  
  @param numberOfBlanksToIndent the number of spaces which is used for indent the XML-structure
  @return the transformer
  
  @since XMLUnit 2.4.0