The enum describing optimize assets subtype.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v26/enums/optimize_assets_experiment_subtype.proto)

| Enums ||
|---|---|
| ## `ADD_ASSETS_TO_ASSETLESS_RETAIL` | The experiment is testing adding assets to assetless retail PMax experiment. |
| ## `ADD_VIDEO_ASSETS_TO_VIDEOLESS` | The experiment is testing adding video assets to videoless PMax experiment. |
| ## `COMPARE_ASSETS` | The experiment is testing comparing two different sets of assets in a PMax experiment. |
| ## `UNKNOWN` | The value is unknown in this version. |
| ## `UNSPECIFIED` | Not specified. |