Okay. So that other idea does not work. TBH, I am not sure I even understand what this instance of caching is trying to save/ accomplish. The following does not even hold:

```
f = pd.DatetimeIndex(start="2013-01", end="2013-03", freq="M")
assert f[0] is f[0]
```

so when i tried this, it also failed:
```
        range1 = DatetimeIndex(start=datetime(2013,1,31), end=datetime(2013,3,29), freq=BusinessMonthEnd(), normalize=True)
        range2 = DatetimeIndex(start=datetime(2013,1,31), end=datetime(2013,3,29), freq=BusinessMonthEnd(), normalize=True)
        self.assertIs(range1[0], range2[0])
```

At this point, I think I will just assert that the cache is not empty.