Refactor matplotlib figure tests for lab 4 #52
Description
In #45 I disabled the matplotlib figure tests, because they assume that the whole notebook is loaded, but due to issue #50 we cannot load all matplotlib figure like it is currently done. For now the tests are disabled for lab 4, but the figures have to be loaded by scrolling through the notebook. This needs just some extra logic, but is not that much work. To speed the lab 4 integration however I put this as a task for later.