How to use the postprocessing.BlendFunction function in postprocessing

constructor(name, options = {}) {
		const fragmentShader = readFileSync(resolve(__dirname, '../../glsl/' + name + '.glsl')).toString();
		options.blendFunction = options.blendFunction || POSTPROCESSING.BlendFunction.NORMAL;

		super(name, fragmentShader, options);
	}
}

focus: 90.0,
            focalLength: 190,
            luminanceThreshold: 0.325,
            luminanceGain: 2.0,
            bias: -0.35,
            fringe: 0.7,
            maxBlur: 50,
            rings: 5,
            samples: 5,
            showFocus: false,
            manualDoF: false,
            pentagon: true
        });

        const bloomEffect = new post_pss.BloomEffect({
            blendFunction: post_pss.BlendFunction.ADD,
            resolutionScale: 0.5,
            distinction: 4.0
        });
        bloomEffect.blendMode.opacity.value = 2.1;


        var bokeh = new post_pss.EffectPass(options.camera, bokehEffect, bloomEffect);
        composer.bokeh = bokeh;
        composer.addPass(bokeh);
        bokeh.renderToScreen = true;
        window.bokeh = bokeh;
    }

    return composer;
}