Core functions for machine learninig and pipeline execution.

Functions are re-exported from:

* scicloj.metamorph.ml.*
* scicloj.metamorph.core

This namespace contains functions which operate on a dataset
and mostly return a dataset.

The namespaces scicloj.ml.metamorph and scicloj.ml.dataset contain
functions with the same name. But they operate on either a context
map (ns metamorph) or on a dataset (ns dataset)

The functions in tis namespace are re-exported from:

* tabecloth.api
* tech.v3.dataset.modelling
* tech.v3.dataset.column-filters

This namespace contains functions, which operate on a metamorph context.
They all return the context as well.

So all functions in this namespace are metamorph compliant and can
be placed in a metamorph pipeline.

Most functions here are only manipulating the dataset, which is in the ctx map
under the key :metamorph/data.
And they behave the same in pipeline mode :fit and :transform.


A few functions manipulate other keys inside the ctx map, and/or behave
different in :fit and :transform.

This is documented per function in this form:

metamorph                            | .
-------------------------------------|------------------------------
Behaviour in mode :fit               | .
Behaviour in mode :transform         | .
Reads keys from ctx                  | .
Writes keys to ctx                   | .



The namespaces scicloj.ml.metamorph and scicloj.ml.dataset contain
functions with the same name. But they operate on either a context
map (ns metamorph) or on a dataset (ns dataset)

The functions in this namesspaces are re-exported from :

* tablecloth.pipeline
* tech.v3.libs.smile.metamorph
* scicloj.metamorph.ml
* tech.v3.dataset.metamorph