def annotate_base_config(obj, override_config, base_config):
    """
    Adds attributes prefixed with __base__<name> with values from the
    base configuration for every attribute that has been overriden.
    """
    for name in override_config.keys():
        value = getattr(base_config, name, None)
        if value:
            setattr(obj, '__base__' + name, value)
