Undocumented Third Parameter Acceptable in Decision Forest Regression Training .compute() function

[raoberman]

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While coding, I discovered that decision_forest_regression_training.compute() function is allowed to take in a third parameter, however, according to the daal4py documentation, only 2 input parameters are allowed: data and dependentVariable - meaning that this third parameter is undocumented. See here: https://intelpython.github.io/daal4py/algorithms.html#daal4py.decision_forest_regression_training.compute

Upon further investigation, placing in a 1-d vertical numpy array as the value for the third parameter, then running the training/prediction for Decision Forest Regression does not impact the prediction results (same result as only data and dependentVariable being inputted).

See pic below (does not error out):

What is the purpose of this third mystery parameter, and why is it undocumented?

My test code: third_param.zip