[Roxen-AS]

Summary

When copying a fitted model with \prophet.diagnostics.prophet_copy(), the model's custom fitting kwargs (\m.fit_kwargs, such as optimization options or sampler parameters) were omitted from the copy constructor and remained an empty dictionary on the cloned instance, unlike other model attributes (\extra_regressors, \seasonalities, \country_holidays, \scaling).

Changes

• In \python/prophet/diagnostics.py: Copy \m.fit_kwargs\ onto \m2.fit_kwargs\ using \deepcopy.
• In \python/prophet/tests/test_diagnostics.py: Added \ est_prophet_copy_fit_kwargs\ verifying that custom \it_kwargs\ are preserved and that mutating the copied dictionary does not alter the original.

Validation

• Syntax and compilation validated with \python -m compileall -q python/prophet/diagnostics.py python/prophet/tests/test_diagnostics.py.
• Clean diff verified with \git diff --check.