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* Initiated ``xai`` subpackage
* Creates base class ``ExplainerMixin`` for all explainers with the **fit** & **explain**
convention (familiar from scikit-learn API).
* Releases, in the development version, the ``xai.FeatureEffectExplainer`` implementing
calculation of **Partial Dependence Plot**, **Individual Conditional Expectation** and
**Marginal Plot**.
* Optimized ``Discretizer``
* Limits the transformations only to continuous variables by not taking into consideration
categorical variables and leaving them unchanged.
* Created optional dependencies
* Reduces the number of dependent packages by creating optional functionalities
that require additional installation of the extra requirements.
* Renamed ``collinearity_reduction`` module
* Changes the module name to ``feature_selection`` to prepare it for future
expansion in this direction.
* Modified ``utils.is_numeric``
* Excludes from checking for numericity categorical pandas.Series.
* Adds the ability to disable the attempt to project on a numeric type.
* Moved ``mathy`` module
* Changes the location of ``mathy`` module to ``utils`` subpackage.
The new location is as follows: ``utils.mathy``.
* Fixed missing values temporary imputation inside the ``VIFSelector``
* Imputs the missing values before checking the NaN condition.