code: public <T> Optional<T> getSubAttrOptional(String attrName, String dPath, Class<T> clazz) {
          return Optional.ofNullable(getSubAttr(attrName, dPath, clazz));
      }
docs: Get a sub-attribute using d-path.
  
  @param attrName
  @param dPath
  @param clazz
  @return
  @since 0.8.0