use Centroid;
use crateObservation;
use crateAbstraction;
use crateHistogram;
use BTreeMap;
/// intermediate data structure to reference during kmeans
/// as we compute the Wasserstein distance between
/// `Observation`s and the available `Abstraction`s > `Centroid`s > `Histogram`s
;
/// intermediate data structure to mutate during kmeans
/// as `Observation`s become assigned to `Abstraction`s.
;