Validate environment variables names.
Validate environment variables names.

PiperOrigin-RevId: 459752261
Change-Id: Icf9e2ea959100cb4bab8a96bee518464f03eda74
GitOrigin-RevId: f3dd768e3ba0c20d246a0e8a3fb3863cfc35dfda

deepmind/xmanager,deepmind/xmanager