In Unison, you do not need to import code. That's because every variable is actually the hash of its definition, and when you use that variable in your code, it automatically "imports" the hash. That also means that your code contains only the variables that you actually use.
You do still lose some correctness, though. As an example, if you have a function and you change the definition of that function, it will create a new hash (for the new definition), but the old hash is still being used in your code.
Which means that you have both the old version of the function and the new version of the function existing at the same time. So you need to manually update all of your code to use the new hash: