ValueError: Need `time` to have same type as `self.durations`

This error happens when using multi-processing. This error is due to this check that happens in line 55:
[https://github.com/havakv/pycox/blob/master/pycox/preprocessing/discretization.py#L155](https://github.com/havakv/pycox/blob/master/pycox/preprocessing/discretization.py#L155)

In my humble opinion, I don't see any reason to use `is not` for validating because a simple `!=` would do the job without checking the identity of the objects.

Start by reading pycox/preprocessing/discretization.py at the validation check linked in the issue, around line 155. Reproduce the multiprocessing case if possible, then verify the validation no longer raises for equivalent duration and time values and that the existing test suite still passes.

Written by the indexing model from the issue text.