do you mean?

```
// Filters the property keys used to serialize a given model.
//
// The default implementation simply returns `propertyKeys`.
//
// propertyKeys - The property keys for which `model` provides a mapping.
// model        - The model being serialized.
//
// Subclasses may override this method to determine which property keys should
// be used when serializing `model`. For instance, this method can be used to
// create more efficient updates of server-side resources.
//
// Returns a subset of propertyKeys that should be serialized for a given
// model.
```