create a mi

In [13]: mi = pd.MultiIndex.from_product([[1,2,3], list('abc'), pd.date_range('20200101', periods=2, tz='UTC')], names=['int', 'string', 'dt'])                            

You can already get .dtypes, but is slightly cumbersome. I would propose adding Multidex.dtypes (we already have MultiIndex.dtype but its always object). I think this is worth the convenience api.

The version of device_copy_n which takes a CUDA stream argument
https://github.com/clara-parabricks/GenomeWorks/blob/74e6424c156a7ee15b4137d4788a4257ee6482c4/common/base/include/claraparabricks/genomeworks/utils/cudautils.hpp#L138
should be renamed to device_copy_n_async to make the non-blocking behavior more obvious.

The blocking three-argument version of device_copy_n should remain