DOC: .bfill() (#46631)
- [x] closes #46631 (Replace xxxx with the Github issue number)
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Thanks @kwhkim - wouldn't this be equivalent of `df.reindex(df.index[::-1]).ffill().reindex(df.index)`?
```
In [7]: df.reindex(df.index[::-1]).ffill().reindex(df.index)
Out[7]: 
                   A
2013-08-01 -1.571201
2013-08-02  2.061834
2013-08-05 -0.831290
2013-08-06  1.448895
2013-08-07  1.448895
2013-08-08 -0.258116

In [8]: df.bfill()
Out[8]: 
                   A
2013-08-01 -1.571201
2013-08-02  2.061834
2013-08-05 -0.831290
2013-08-06  1.448895
2013-08-07  1.448895
2013-08-08 -0.258116
``` Yes, I just meant that the contents are the same. Would it be better to be `df.reindex(df.index[::-1]).ffill().reindex(df.index)`? The context is talking about `df.reindex(df.index[::-1]).ffill()` so I think it might be better to change `df.bfill()` to `df.bfill().reindex(df.index[::-1])` considering the paragraph it's in. I think just put
```
df.bfill()
```
without the comment and it'll be fine

cc @jreback , who originally wrote this example thanks @kwhkim 