ds-8.x-3.9/tests/modules/ds_test/config/schema/ds_test.schema.yml

ds.field_template.ds_test_template:
  type: config_object
  label: 'The settings of the ds_test_theming_function field template'
  mapping:
    lb:
      type: string
      label: 'The label of the field'
    lb-col:
      type: boolean
      label: 'Enable the label colon'
    classes:
      type: sequence
      label: 'Classes for the template'
      sequence:
        type: string
        label: 'Class name'

layout_plugin.settings.ds.dstest_1col_extended:
  type: ds.layout_plugin.settings.default
  mapping:
    extra_config:
      type: boolean
      label: 'Extra config'