as_block depr warning on tab completion
```
In [13]: df = pd.Series([1, 2, 3])

In [14]: df.<TAB>
/Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/pandas/pandas/core/generic.py:3720: FutureWarning: as_blocks is deprecated and will be removed in a future version
  return self.as_blocks()
```

This came up before in https://github.com/pandas-dev/pandas/issues/16409 and the fix is in https://github.com/pandas-dev/pandas/pull/16414