Let's do it 'right'.

Step 1: Write class design in the form of a class with methods with APIs and docstrings as the bodies.

class Changes:
   """Manage a user's proposed configuation option changes.

   Changes are either cancelled or applied in a single transaction.
   Methods used by ConfigDialog:
   meth_a does xa
   Methods used only for testing (if any)
   meth_t does xt for testing
   Internal methods not called externally:
   meth_b does xb.
   """

   def __init__(self, ???):  # new
   """Create configuration option change manager.

   arg: bool, do we like George Boole?
   """

Temporarily comment methods as new, old, renamed from whatever.

Step 2. Test design by writing a test class with at least a few test methods.  If methods are not easy to write, perhaps we should change design.

class ChangesTest(unittest.TestCase):
# no gui needed.    

Step 3. Write simple, clear bodies that make tests pass.

However much you submit, I will review in that order: design, tests, implementation.