Gio.Settings.settings_schema

Settings.settings_schema: Gio.SettingsSchema (Read / Write / Construct Only)
  

The Gio.SettingsSchema describing the types of keys for this Gio.Settings object.

Ideally, this property would be called 'schema'. Gio.SettingsSchema has only existed since version 2.32, however, and before then the 'schema' property was used to refer to the ID of the schema rather than the schema itself. Take care.