Can't specify --cgroup-parent when building images.

[waynr]

I don't see documentation for this anywhere on https://docker-py.readthedocs.io/en/stable/index.html

If I can dredge up the motivation after work I'll look into submitting a PR for this.

[Khushiyant]

@shin- @waynr It is possible to override default cgroup-parent - refer here