Transformer.ProgressState (ExoPlayer library)

```
@Documented
@Retention(SOURCE)
@Target(TYPE_USE)
public static @interface Transformer.ProgressState
```
Progress state. One of Transformer.PROGRESS_STATE_NOT_STARTED, Transformer.PROGRESS_STATE_WAITING_FOR_AVAILABILITY, Transformer.PROGRESS_STATE_AVAILABLE or Transformer.PROGRESS_STATE_UNAVAILABLE.