LoadAssetFromPathWithSubAssets.cs

public static IEnumerable<Object> LoadAssetsFromPathWithSubAssets(this IEnumerable<string> paths)
{
    foreach (var path in paths)
    {
        var assets = AssetDatabase.LoadAllAssetsAtPath(path);
        if (assets == null || assets.Length == 0)
        {
            yield return AssetDatabase.LoadAssetAtPath<Object>(path);
            yield break;
        }
        foreach (var asset in assets)
            yield return asset;
    }
}