public IClientConfig applyOverride(IClientConfig override) {
        if (override == null) {
            return this;
        }

        override.forEach((key, value) -> setProperty(key, value));

        return this;
    }
Store the default value for key while giving precedence to default values in the property resolver
ribbon-core/src/main/java/com/netflix/client/config/ReloadableClientConfig.java