Subclass of `BaseManager` which supports a number of shared object types.
The types registered are those intended for the synchronization
of threads, plus `dict`, `list` and `Namespace`.
The `multiprocessing.Manager()` function creates started instances of
this class.
3.6: Shared objects are capable of being nested. For example, a shared container object such as a shared list can contain other shared objects which will all be managed and synchronized by the SyncManager.