This is the place with the weird loopback definition between `SyncedModel` (and sorry--other models as well) and `Device`.  They all referenced Device for get_own_device().  My solution was to define this global _get_own_device() function, which could import Device on the fly when needed, thus breaking the import loop.

The other place where there were references were in ForeignKey definitions.  Fortunately, these seem to be resolved dynamically, on-demand, which again breaks any possible import loop.