I’ve got a matrix in my model block:

```
matrix[3,5] x;
```

Which I need to pass to `cov_exp_quad`

, which expects an array of vectors, i.e.:

```
vector[5] x[3];
```

Is there a simple way to convert it, something like to_vector? If x was in the data block it would be fine, but x results from some linear algebra operations so I think it has to be a matrix.