Add assertions public api methods

[arnaudde]

First draft of methods to be added is in the wiki
Can be tested with the dip pr that adds tests for the methods added in this PR.

[instanceofme]

Looks better. A few wording / readability nitpicks.

[arnaudde]

As fred T explained ~ in class reference are for sphynx syntax display purposes. I am using simple strings without path as everything is in the same package.

https://www.sphinx-doc.org/en/master/usage/restructuredtext/roles.html
If you prefix the content with ~, the link text will only be the last component of the target. For example, :py:meth:~Queue.Queue.get will refer to Queue.Queue.get but only display get as the link text. This does not work with all cross-reference roles, but is domain specific.

[arnaudde]

Methods are working (no failure, result looks good) on a python3.6 notebook

[instanceofme]

Essentially LGTM

[nicolasservel]

Last nitpicks on formatting docstring, otherwise the API works smoothly :-)