The latest release of transitionMatrix library (0.4.7) expands the documentation and example set. The Academy Course PYT26038 (Analysis of Credit Migration using Python TransitionMatrix) that takes you step by step through the basics of using the library. There are five steps (course sections) that cover the main functionality of the TransitionMatrix package, with applications to a variety of synthetic and real credit data. The examples used in the course are also available in the github repository (for those who do not like to type :-)
A little bonus: Sankey diagrams are very useful for the visualization of flows, especially when there is a conserved quantity. They can be tricky when some of the flows are much smaller than others such as is typically the case with credit rating transitions. In the latest release of transitionMatrix we include an example of a log-scale version of Sankey