GitLab

* format timesteps attrs to np arrays in pndm scheduler
because lists don't get formatted to tensors in `self.set_format`

* convert to long type to use timesteps as indices for tensors

* add scheduler set_format test

* fix `_timesteps` type

* make style with black 22.3.0 and isort 5.10.1
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>