A fixed-point function returning an attribute set has the form
```nix
final: { # attributes }
final: {
# attributes
}
```
where `final` refers to the lazily evaluated attribute set returned by the fixed-point function.
@@ -168,7 +170,9 @@ rec {
An overlay to such a fixed-point function has the form
```nix
final: prev: { # attributes }
final: prev: {
# attributes
}
```
where `prev` refers to the result of the original function to `final`, and `final` is the result of the composition of the overlay and the original function.