docs: public void loadSubjectScheme(final File scheme) {
          assert scheme.isAbsolute();
          if (!scheme.exists()) {
              throw new IllegalStateException();
          }
          logger.debug("Load subject scheme " + scheme);
  
          try {
              final DocumentBuilder builder = XMLUtils.getDocumentBuilder();
              final Document doc = builder.parse(scheme);
              final Element schemeRoot = doc.getDocumentElement();
              if (schemeRoot == null) {
                  return;
              }
              loadSubjectScheme(schemeRoot);
          } catch (final RuntimeException e) {
              throw e;
          } catch (final Exception e) {
              logger.error(e.getMessage(), e) ;
          }
      }