Printing empty stuff1 set ......: {}

Printing the entire stuff2 set..: {1, 2, 3, 4, 5, 6, 7, 8, 9}
The number of elements in stuff2: 9

Printing the entire stuff3 set..: {1, 2, 3, 'Steve', 'John', 'Sam'}
After add, and delete ..........: {1, 2, 3, 'Steve', 4, 'Bill', 'John'}