flattenAssets(stats) {
        let assets = Object.assign({}, stats.assetsByChunkName);

        // If there's a temporary mix.js chunk, we can safely remove it.
        if (assets.mix) {
            assets.mix = collect(assets.mix).except('mix.js').all();
        }

        return (
            collect(assets)
                .flatten()
                // Don't add hot updates to manifest
                .filter(name => name.indexOf('hot-update') === -1)
                .all()
        );
    }
Flatten the generated stats assets into an array.

@param {Object} stats