Learn how to query an Immutable.Map() using get, getIn, has, includes, find, first and last. These are powerful operators that make finding data in an object graph pain free.
The official immutable.js docs are impossible to read, that is why people come here.
But instead of learning how these functions work we're covering wrappers, abstractions and tests.
I really wish you would have just used the functions as they are, show what they return, thereby cutting the lessons time in half. Right now i am not sure if i better crawl through robotic typescript definitions than watch yet another test that calls this and that wrapper named differently than the immutable method way outside the view comparing results not shown.