* @param transformer the instance used to transform values
* @param fields the paths to the fields you want to transform. They can be in dot notation.
* @return Hit you back with the JSONSerializer for method chain goodness.
*/
public JSONSerializer transform(Transformer transformer, String... fields) {
transformer = new TransformerWrapper(transformer);
for (String field : fields) {
if (field.length() == 0) {
pathTransformerMap.put(new Path(), transformer);
} else {
pathTransformerMap.put(new Path(field.split("\\.")), transformer);