exemplars - provide a better overview from the start

[dpshelio]

The exemplars provided at the start of each section are good, however, we've found they are not great as they are to show them in class.

A diagram/flowchart summarising the steps before the code is show may help the learners to get the big picture first.

[dpshelio]

As @matt-graham has well described, the first exemplar follows as a series of explorations of the data rather than following a structured sequence of steps towards some pre-defined goal. We may need to change the exemplar a bit in order to be able to give a better overview first.