[apparmor] How to extend an existing profile?

[Forest]

I need my custom AppArmor profile to mimic one of those included with LXC,
with a new name and a few additional rules.  Is there a way to do this
without copying the contents of the upstream profile?  Some way for one
profile to inherit the rules of another profile?

I considered #include, but that looks like a simple text import that would
pull in the whole upstream file, including its header, and therefore not
work.

As a last resort, I suppose I could copy the upstream profile's contents
into a new file along with my additions, but that would duplicate upstream
policy and risk falling out of sync with upstream changes.

The use case is to get Steam's pressure-vessel working in LXC containers.