ML4SCI/DeepLenseSim/Model-4 ImportError for CDM and ULDM with newer pyHalo versions

[Shrishagk]

While testing Model IV, I encountered ModuleNotFoundError and ImportError for CDM and ULDM imports. This appears to be due to API changes in newer versions of pyHalo. This issue tracks the implementation of version-agnostic factory imports to ensure compatibility.

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##Proposed Fix
Replace the original import code with a try and except code block

try:
    from pyHalo.preset_models import preset_model_from_name
    # Use the factory function to get ULDM
    ULDM = preset_model_from_name('ULDM')
except Exception as e:
    # If that also fails, we'll need to see the specific error
    print(f"Failed to load ULDM: {e}")
    raise

---

Note:

1. I tested using the latest commits from Fix hardcoded absolute paths in simulation scripts mwt5345/DeepLenseSim#1 (PR branch), since the fixes are not merged into main yet.
2. Even after resolving imports, the scripts sim_cdm.py and sim_no_sub.py fail with a FileNotFoundError for Galaxy10_DECals.h5.

[Aryanpagaria]

@Shrishagk @rchudasa can i work on this issue
This is my approach
My plan is to make the imports version-agnostic by:
Replacing direct CDM / ULDM imports with the factory-based
preset_model_from_name interface where available
Falling back to the legacy import paths via try/except to preserve backward compatibility

In addition, I noticed that after resolving the import errors, the scripts
sim_cdm.py and sim_no_sub.py fail due to a missing
Galaxy10_DECals.h5 file. I plan to:
Verify whether this dataset is expected to be user-provided or bundled
Add clearer error handling and documentation, or a configurable path, to avoid silent failures

[Shrishagk]

Hi @Aryanpagaria ,I have already linked a pr for this issue.You can check the pr and address any changes if needed.

[ApurvaPatil2401]

Hi! I'm a Master's graduate. I've just successfully contributed to the Mesa project and would like to help resolve this ImportError with Model-4 and pyHalo. I'm setting up my environment now to reproduce the error.

[ApurvaPatil2401]

I've submitted a PR to fix the pyHalo import issues and the arguments in lens.py. The simulation script is now functional.