corrected Type Error on process_worker_pool.py

[christailu]

Description

This PR enhances argument handling in the process_worker_pool.py script by making the --available-accelerators parameter optional with a default value. Additionally, it adds validation for the --cpu-affinity parameter and ensures that the MPI launcher is provided when MPI mode is enabled.

Changed Behaviour

After this PR, users can run the process_worker_pool.py script without providing the --available-accelerators argument. If not provided, it defaults to an empty list, indicating zero accelerators available. Furthermore, the script now validates the --cpu-affinity parameter to ensure it contains a valid value, and it enforces the requirement of providing the MPI launcher when MPI mode is enabled.

Fixes

Fixes # (issue)

Type of change

Choose which options apply, and delete the ones which do not apply.

• Bug fix

[christailu]

Hello @benclifford , can you take a look at what I have made and please give me some feedback on what I can improve thanks!