Docker API: List Volumes: How to deal with the Warnings member?

Hi,

the List Volumes command (GET /volumes) provides an object with the members Volumes and Warnings. Happy with the Volumes member, but I can’t find any detailed information about the Warnings member in the docs.

Does anyone know, what they look like when they appear and, even better, how one can provoke those warnings for testing?

Regards,

Carsten