docs: private static void handleSingletonList(String key, List<Object> value) throws Exception {
  
          List<String> interfaceClasses = new ArrayList();
          if(key.contains(",")) {
              String[] interfaces = key.split(",");
              interfaceClasses.addAll(Arrays.asList(interfaces));
          } else {
              interfaceClasses.add(key);
          }
          // the value can be a list of implementation class names or a map.
          if(value != null && value.size() == 1) {
              handleSingleImpl(interfaceClasses, value);
          } else {
              handleMultipleImpl(interfaceClasses, value);
          }
      }