docstring templates not being filled
```
>>> print(pd.DatetimeIndex.fillna.__doc__)

Fill NA/NaN values with the specified value

Parameters
----------
value : scalar
    Scalar value to use to fill holes (e.g. 0).
    This value cannot be a list-likes.
downcast : dict, default is None
    a dict of item->dtype of what to downcast if possible,
    or the string 'infer' which will try to downcast to an appropriate
    equal type (e.g. float64 to int64 if possible)

Returns
-------
filled : %(klass)s
```

I'm pretty sure that the `%(klass)s` is supposed to be `DatetimeIndex`.