Pandas for Finance AttributeError: 'DataFrame' object has no attribute 'rolling'
#### Code Sample, a copy-pastable example if possible

rets.rolling(window=22).min().plot.line(figsize=(15,10))
#### Expected Output
#### output of `pd.show_versions()`

Traceback (most recent call last):

  File "<ipython-input-78-e1069c24fa37>", line 1, in <module>
    rets.rolling(window=22).min().plot.line(figsize=(15,10))

  File "C:\Users\LastAncientOne\Anaconda3\lib\site-packages\pandas\core\generic.py", line 2360, in **getattr**
    (type(self).**name**, name))
