Is there something smarter than can be done here? For example using something similar to what I did in test_offsets:
```python
def get_all_subclasses(cls):
    ret = set()
    this_subclasses = cls.__subclasses__()
    ret = ret | set(this_subclasses)
    for this_subclass in this_subclasses:
        ret | get_all_subclasses(this_subclass)
    return ret

def make_mapping():
        for subclass in get_all_subclasses(CacheableOffset):
            if subclass.__name__[0] == "_" \
                or subclass in TestCaching.no_simple_ctr:
                continue
            #Add subclass.prefix to map
```