bug in the covariance. Took the covariance_a_posteriori instead of the

See merge request !37

covariance.

Dev

See merge request !36

rewrite how we create the tests for docstrings (and added for the

See merge request bbatardiere/pyplnmodels!35

needs an image of jupyter notebook and a little preprocessing to remove
the pip install line.

cells.

readme). Now they will al be performed by pytest.