Support persistence when code is imported w/ importlib module

[shaypal5]

@shaoyucheng used cachier directly in his business code, and found it was not working. He then set up some test code to verify, and it worked well as expected. He finally found the key point was his business code was running through importlib module and the underlying framework codes generated a uuid for every module imported at every running time which disturbed the unique module name obtained by cachier.

1. It's a point worthy of attention if your running mechanism is similar to his.
2. It might be worthwhile supporting this functionality.