Overview of how the ray images are built:

Images without a "-cpu" or "-gpu" tag are built on ubuntu/focal. They are just an alias for -cpu (e.g. ray:latest is the same as ray:latest-cpu).

ubuntu/focal
└── base-deps:cpu
    └── ray-deps:cpu
        └── ray:cpu
            └── ray-ml:cpu

nvidia/cuda
└── base-deps:gpu
    └── ray-deps:gpu
        └── ray:gpu
            └── ray-ml:gpu