QST: why do we compute hash here
- [x] I have searched the [[pandas] tag](https://stackoverflow.com/questions/tagged/pandas) on StackOverflow for similar questions.

- [ ] I have asked my usage related question on [StackOverflow](https://stackoverflow.com).

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#### Question about pandas

In pandas.core.indexes.base ``hash`` is called [here](https://github.com/pandas-dev/pandas/blob/a09259b5699b0f2667761356cb3b22ef43ef37f0/pandas/core/indexes/base.py#L4118) and the value is not used. 

Why is this done?
