I'm trying to create a Migrate group with following code. But it is not detected & listed in admin/structure/migrate. Both migrate plus & Migrate tools modules are installed. I"m trying to create migration from WordPress tables. The module is called migrate_wordpress & migrate group is defined in config/install with the name migrate_wordpress. migrate_group.wordpress.yml

id: wprdpress
label: WordPress Imports
description: Import from WordPress blog
source_type: Custom tables

What is wrong with above Migrate group configurations? What is the correct way to write an migrate group configuration file in Drupal 8?