docs: def get_schema(self, protocol_version):
          """Return the child schema for the correct const version."""
          const = get_const(protocol_version)
          custom_schema = vol.Schema({
              typ.value: const.VALID_SETREQ[typ]
              for typ in const.VALID_TYPES[const.Presentation.S_CUSTOM]})
          return custom_schema.extend({
              typ.value: const.VALID_SETREQ[typ]
              for typ in const.VALID_TYPES[self.type]})