See Dockerfile reference at https://docs.docker.com/engine/reference/builder/#format
object
Other instruction classes: Add-class,
Arg-class, Cmd-class,
Copy-class, Entrypoint-class,
Env-class, Expose-class,
From-class,
Healthcheck-class,
Instruction-class,
Label-class,
Maintainer-class,
Onbuild-class, Run-class,
Run_shell-class, Shell-class,
Stopsignal-class,
Volume-class, Workdir-class