We were using the same code, and the same regular expressions, in two
places. To do so, we were including a helper inside a model, which is
something we don't usually do.
We were inconsistent on this one. I consider it particularly useful when
a method starts with a `return` statement.
In other cases, we probably shouldn't have a guard rule in the middle of
a method in any case, but that's a different refactoring.
