fix for multiple files in a stream config in msds

[shmh40]

Description

Previous msds wouldn't read multiple files in the stream config. Think this fixes it...

Issue Number

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Checklist before asking for review

• I have performed a self-review of my code
• My changes comply with basic sanity checks:
  • I have fixed formatting issues with ./scripts/actions.sh lint
  • I have run unit tests with ./scripts/actions.sh unit-test
  • I have documented my code and I have updated the docstrings.
  • I have added unit tests, if relevant
• I have tried my changes with data and code:
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  • (bigger changes) I have run a full training and I have written in the comment the run_id(s): launch-slurm.py --time 60
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