I’ve hit a problem setting the standard deviations for a multilevel multinomial model.

My problem is something like

```
formula <- y | trials(total) ~ (1 + year || region\country) + (-1 + covariate | region)
priors <- c( set_prior("normal(0,1)", class = "b"),
set_prior("normal(0,1)", class = "sd"))
code <- make_stancode( formula , data = analysis_data, prior=priorsl)
```

throws the error

```
rror: The following priors do not correspond to any model parameter:
sd ~ normal(0,1)
Function 'get_prior' might be helpful to you.
```

The function `get_prior`

does not help :p

If I try

```
priors <- c( set_prior("normal(0,1)", class = "b"),
set_prior("normal(0,1)", class = "sd", group = "region"))
```

I get the same error except it says that `sd_region`

does not exist.

Any ideas?

(Edit: this is brms version 2.10.0)