Best pattern to avoid module globals from being cleaned up

Question

I'm finding that some modules that defined global objects are re-created when the module is import later:

# mymodule
pool = MyPoolObject()

and if accessed from some code:

def f():
   from mymodule import pool
   print id(pool)

Subsequent calls to f print different ids! This is surprising. I expect that when f exits, its the last reference to mymodule and the global is unloaded. I can't for a reference to mymodule in the caller of f, because, ultimately its an RPC service that doesn't know what modules it will be calling (it receives pickled objects and calls them).

Is there a good way to avoid this behavior and keep the globals from being unloaded? One quick workaround is to add a reference in sys:

# mymodule
import sys
sys._mymodule_pool = MyPoolObject()
pool = sys._mymodule_pool

... but even this doesn't seem like it wouldn't guarantee that its not unloaded.