Type tweak: Allow ZarrMonitor to take in Comm | DummyComm | None

[jjuyeonkim]

Description

Small proposed type adjustment for the Zarr Monitor. Without this, there are type linting errors when attempting to update the submodules for Pace: NOAA-GFDL/pace#156

How has this been tested?

CI passes, linting passes in Pace locally with this update

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (e.g. add new modules to docs/docstrings/)
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included

[jjuyeonkim]

I think an alternative could be to try having mpi_comm: Comm | None = None. Then, maybe have DummyComm inherit from Comm.

[romanc]

yeah, ZarrMonitor should allow any Comm object and DummyComm should inherit from Comm. I made an alternative PR in #292.