Revert "Changed to make the second challenge example relevant to the overall example. I also changed the first, second to be item, value tuples(which could be key value pairs in another situations). Now the example demonstrates how you might reverse the key value pair. That is, in one situation they key might be Disease an the value Arthritis, but in another situation the Key might be Arthritis and the value disease."

This reverts commit 948d3b8ce5485fb0e5f8aa5a8eee962451bc0168.
Changed to make the second challenge example relevant to the overall example. I also changed the first, second to be item, value tuples(which could be key value pairs in another situations). Now the example demonstrates how you might reverse the key value pair. That is, in one situation they key might be Disease an the value Arthritis, but in another situation the Key might be Arthritis and the value disease. SECOND TIME