code: public static PrefsTransform lookup(TypeName typeName) {
  		PrefsTransform transform = cache.get(typeName);
  
  		if (transform != null) {
  			return transform;
  		}
  
  		transform = getTransform(typeName);
  		AssertKripton.assertNotNull(transform, new UnsupportedFieldTypeException(typeName));		
  		cache.put(typeName, transform);
  
  		return transform;
  	}
docs: Get transformer for type.
  
  @param typeName the type name
  @return transform