code: @SuppressWarnings("unchecked") public <V> Mapper<String, V> mapper() {
  		if (!isChanged && nameValMap.isPresent()) {
  			return (Mapper<String, V>) nameValMap.get();
  		}
  		
  		Map<String, Object> fm = Maps.newHashMap();
  		if (fieldHolder.isPresent()) {
  			fieldLoop(new TransformFields2Map<Object>(fm, this.trace));
  		}
  		nameValMap = Optional.of(Mapper.from(fm));
  		
  		this.isChanged = false;
  		return (Mapper<String, V>) nameValMap.get();
  	}
docs: Returns delegate object instance as a {@link Mapper}
  
  @return