Adapter to dump/load YAML format strings and files.
        
        Returns:
            ConfigPersistenceAdapter

def yaml(self):
        """
        Adapter to dump/load YAML format strings and files.
        
        Returns:
            ConfigPersistenceAdapter
        """
        if self._yaml_adapter is None:
            self._yaml_adapter = ConfigPersistenceAdapter(
                config=self,
                reader_writer=YamlReaderWriter(),
            )
        return self._yaml_adapter