See #36285 which mistakenly added documentation for the whole C++ API, while
some of it is meant to be and stay private as it's not exposed to scripts.
The access modifiers and method prefix were not used properly.
Cleanup code, and rename wrong `group_name` parameters to `method`, as it's a
method name which is being broadcast.
This is a very old class from pre-open source days, chances are that it was
just forgotten and not meant to be kept as is and undocumented.
