Async RecordSource methods mentioned in docs but don't seem to exist

Hi, the documentation [here](https://relay.dev/docs/principles-and-architecture/runtime-architecture/#data-types) mentions:

> RecordSource (type): A collection of records keyed by their data ID, used both to represent the cache and updates to it. For example the store's record cache is a RecordSource and the results of queries/mutations/subscriptions are normalized into RecordSources that are published to a store. **Sources also define methods for asynchronously loading records in order to (eventually) support offline use-cases.** Currently the only implementation of this interface is RelayInMemoryRecordSource; future implementations may add support for loading records from disk.

But the `RecordSource` interface doesn't define async methods, nor any of the child interfaces.

Could someone please help me understand if the documentation is outdated/wrong, or if I'm missing something?