Drop rows based on condition
Here are 2 ways to drop rows from a pandas data-frame based on a condition:

1. `df = df[condition]`

2. `df.drop(df[condition].index, axis=0, inplace=True)`

The first one does not do it *inplace*, right?

The second one does not work as expected when the index is not unique, so the user would need to `reset_index()` then `set_index()` back. 


**Question**
Would it be possible to have column dropping based directly on the condition?
e.g.
`df.drop(condition, axis=0, inplace=True)`
