Adding doctests into LDA algorithm (#1621)

* Adding doctests into <gaussian_distribution> function

* Adding doctests into <y_generator> function

* Adding doctests into <calculate_mean> function

* Adding doctests into <calculate_probabilities> function

* Adding doctests into <calculate_variance> function

* Adding doctests into <predict_y_values> function

* Adding doctests into <accuracy> function

* fixup! Format Python code with psf/black push

* Update convex_hull.py

* Update convex_hull.py