All examples in episode 4 ("Returning Output Files") and onward must have outputs

[mr-c]

1. To demonstrate good practice
2. To enable testing of the docs

Specific list: episodes 7, 9, 11 (2nd and 3rd examples), 12, 13 and 14

[mr-c]

Thanks to @tom-tan for alerting us: #61 (comment)

[mr-c]

Done!