Translation in subfolder

[StefanoTesla]

I would like to organize my translations in subfolders to keep it more organized...

lang\it\seo\file.php

i tried to retrive a string from there in a lot of way:

{{ __(seo.file.string) }} html render: seo.file.string

{{ __(seo\.file.string) }} html render: seo.file.string
{{ __(seo\file.string) }} php fatal error array_replace_recursive(): Argument #2 must be of type array, int given
{{ __(seo/.file.string) }} html render: seo/.file.string
{{ __(seo/file.string) }} php fatal error array_replace_recursive(): Argument #2 must be of type array, int given

Olso using trans directive same problem..any advice?