docs: public PMML loadModel(String model, InputStream source) {
          try {
              if (schema == null) {
                  visitorBuildResults.add(new PMMLWarning(ResourceFactory.newInputStreamResource(source), "Could not validate PMML document, schema not available"));
              }
              final JAXBContext jc;
              final ClassLoader ccl = Thread.currentThread().getContextClassLoader();
              XMLStreamReader reader = null;
              try {
                  Thread.currentThread().setContextClassLoader(PMML4Compiler.class.getClassLoader());
                  Class c = PMML4Compiler.class.getClassLoader().loadClass("org.dmg.pmml.pmml_4_2.descr.PMML");
                  jc = JAXBContext.newInstance(c);
                  XMLInputFactory xif = XMLInputFactory.newFactory();
                  xif.setProperty(XMLInputFactory.IS_SUPPORTING_EXTERNAL_ENTITIES, false);
                  xif.setProperty(XMLInputFactory.SUPPORT_DTD, true);
                  reader = xif.createXMLStreamReader(source);
  			} finally {
                  Thread.currentThread().setContextClassLoader(ccl);
              }
              Unmarshaller unmarshaller = jc.createUnmarshaller();
              if (schema != null) {
                  unmarshaller.setSchema(schema);
              }
  
              if (reader != null) {
                  return (PMML) unmarshaller.unmarshal(reader);
              } else {
              	this.results.add(new PMMLError("Unknown error in PMML"));
              	return null;
              }
          } catch (ClassNotFoundException | XMLStreamException | JAXBException e) {
              this.results.add(new PMMLError(e.toString()));
              return null;
          }
      }