Arg-instruction class yet to be implemented
object
Other instruction classes: Add-class,
Cmd-class, Comment-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
#no example yet