add_filter(
    'mastodon_api_status_source',
    function (
        Enable_Mastodon_Apps\Entity\Status_Source $status_source = null,
        int $source_id
    ) {
        // Your code here
        return $status_source;
    },
    10,
    2
);

apply_filters( 'mastodon_api_status_source', null, $source_id )