rename imputer classes

[ojassharma7]

Fixes #971.

What changed

• feature_engine/datasets/titanic.py
• feature_engine/imputation/__init__.py
• feature_engine/imputation/arbitrary_number.py
• feature_engine/imputation/mean_median.py
• feature_engine/imputation/missing_indicator.py
• tests/check_estimators_with_parametrize_tests.py
• tests/test_imputation/test_arbitrary_number_imputer.py
• tests/test_imputation/test_check_estimator_imputers.py
• tests/test_imputation/test_mean_median_imputer.py
• tests/test_imputation/test_missing_indicator.py

Verification

The project's own test suite was run before and after this change; it introduces no new test failures or lint violations.

[solegalli]

Hi @ojassharma7

Thanks a lot for your contribution.

We need to split this PR into 3, one per class.

We also need to update the documentation relevant for each transformer, which you'll find inside the docs folder. Basically, we need to replace all calls to the old transformer names by the new transformer names.

We also need to rename files from if necessary, for example if a file was called meanmedianimputer.py or .rst, we need to rename that to the new name of the transformer.

There is also this PR that adds the same changes #972, so maybe you could start with MeanMedianImputer, and we take it from there?

[ojassharma7]

Hi @solegalli — thanks for the guidance!

I'll split this into separate PRs as requested and start with MeanMedianImputer → MeanImputer (including docs / file renames). I'll open that as a new PR shortly and leave the other two classes for follow-ups so we don't overlap with #972.

[ojassharma7]

Follow-up: opened #975 with the MeanMedianImputer → MeanImputer rename only (code + tests + docs / file renames), as discussed.

I'll keep this PR (#973) as a draft / close it once #975 is the path forward, and open separate PRs later for AddMissingIndicator and ArbitraryNumberImputer if they are still needed after #972.