Hello,

I have a beta regression where I model both the response and the dispersion, like this:

```
mean.spec <- as.formula(y ~ ...)
disp.spec <- as.formula(~ ...)
fit <- brm(bf(mean.spec, phi=disp.spec), family=Beta(), ...)
```

The model fits fine, but when I try to see what dispersion is taken at each observation:

```
predict(fit, resp="phi")
```

I get back predictions of the response, i.e. the `resp`

argument is ignored.

This is likely something quite trivial, but I am stumped. Thank you very much in advance.

Versions:

- Operating System: Windows 10
- brms: 2.9.0