2.1.0 version with node and jest mocking causes errors #145

When upgrading to the newest versions of tslib, typescript, and jest I received the following error in an existing project:

TypeError: Cannot redefine property: upsertThing
        at Function.defineProperty (<anonymous>)

 jest.spyOn(transactionDomain, 'upsertThing');

upsertThing is a function exported from it's own file, then again exported from an index file via export *.... When jest tries to spy on it, this error is thrown with version 2.1.0 of tslib. But when I downgrade to tslib 1.14.1 the error goes away.

Version Info:
Node: Tried on both 12 and 14
jest: 26.6.3
ts-jest: 26.4.4
ts-node: 9.1.1
typescript: 4.1.3