# Weird output for differential of a non-analytic complex function.

The following code,

```
var('z')
f = z*z.conjugate()
f.derivative(z)
```

produces

```
z*D[0](conjugate)(z) + conjugate(z)
```

Now I undestand where the problem might be, $z$ and $z^*$ are usually treated as independent variables thus. But does sage mean by this output?