Convert sample_stats_prior samples to xarray.

def sample_stats_prior_to_xarray(self):
        """Convert sample_stats_prior samples to xarray."""
        data = self.sample_stats_prior
        if not isinstance(data, dict):
            raise TypeError("DictConverter.sample_stats_prior is not a dictionary")

        return dict_to_dataset(data, library=None, coords=self.coords, dims=self.dims)