code: public static <T extends Enum<T> & Defaultable> PropertiesManager<T> newManager(File file,
                                                                                      Class<T> keyType,
                                                                                      final Retriever... retrievers)
      {
          return newManager(file, keyType, createExecutor(), retrievers);
      }
docs: Build a new manager for the given properties file.
  
  @param <T>
  the type of key used for the new manager
  
  @param file
  the file system location of the properties represented here
  @param keyType
  the enumeration of keys in the properties file
  @param retrievers
  a set of retrievers that will be used to resolve extra
  property references (i.e. if a nested value reference is found
  in a properties file and there is no property to match it, the
  given retrievers will be used)
  @return a new manager