How to use the webgl-operate.DefaultFramebuffer function in webgl-operate

protected onInitialize(context: Context, callback: Invalidate,
        /* mouseEventProvider: MouseEventProvider, */
        /* keyEventProvider: KeyEventProvider, */
        /* touchEventProvider: TouchEventProvider */): boolean {

        /* Create framebuffers, textures, and render buffers. */

        this._defaultFBO = new DefaultFramebuffer(this._context, 'DefaultFBO');
        this._defaultFBO.initialize();
        this._defaultFBO.bind();

        /* Create and configure test navigation. */

        this._camera = new Camera();

        /* Create and configure label pass. */

        this._labelPass = new LabelRenderPass(context);
        this._labelPass.initialize();
        this._labelPass.camera = this._camera;
        this._labelPass.target = this._defaultFBO;
        this._labelPass.depthMask = true;

        FontFace.fromFile('./data/opensans2048p160d16.fnt', context)

protected onInitialize(context: Context, callback: Invalidate,
        /* mouseEventProvider: MouseEventProvider, */
        /* keyEventProvider: KeyEventProvider, */
        /* touchEventProvider: TouchEventProvider */): boolean {

        /* Create framebuffers, textures, and render buffers. */

        this._defaultFBO = new DefaultFramebuffer(this._context, 'DefaultFBO');
        this._defaultFBO.initialize();

        /* Create and configure test navigation. */

        this._camera = new Camera();

        /* Create and configure label pass. */

        this._labelPass = new LabelRenderPass(context);
        this._labelPass.initialize();
        this._labelPass.camera = this._camera;
        this._labelPass.target = this._defaultFBO;
        this._labelPass.depthMask = false;

        FontFace.fromFile('./data/opensans2048p160d16.fnt', context)
            .then((fontFace) => {

protected onInitialize(context: Context, callback: Invalidate, mouseEventProvider: MouseEventProvider,
        /* keyEventProvider: KeyEventProvider, */
        /* touchEventProvider: TouchEventProvider */): boolean {

        /* Create framebuffers, textures, and render buffers. */

        this._defaultFBO = new DefaultFramebuffer(this._context, 'DefaultFBO');
        this._defaultFBO.initialize();

        /* Create and configure test navigation. */

        this._camera = new Camera();
        this._camera.eye = vec3.fromValues(0.0, 0.0, 1.0);
        this._camera.center = vec3.fromValues(0.0, 0.0, 0.0);
        this._camera.up = vec3.fromValues(0.0, 1.0, 0.0);
        this._camera.near = 0.1;
        this._camera.far = 4.0;

        this._navigation = new Navigation(callback, mouseEventProvider);
        this._navigation.camera = this._camera;

        /* Create and configure label pass. */

protected onInitialize(context: Context, callback: Invalidate,
        mouseEventProvider: MouseEventProvider,
        /* keyEventProvider: KeyEventProvider, */
        /* touchEventProvider: TouchEventProvider */): boolean {

        const gl = this._context.gl;

        this._framebuffer = new DefaultFramebuffer(this._context, 'DefaultFBO');
        this._framebuffer.initialize();

        /* Create mesh rendering program. */
        const vert = new Shader(this._context, gl.VERTEX_SHADER, 'mesh.vert');
        vert.initialize(require('./data/mesh.vert'));
        const frag = new Shader(this._context, gl.FRAGMENT_SHADER, 'mesh.frag');
        frag.initialize(require('./data/mesh.frag'));

        this._program = new Program(this._context, 'MeshProgram');
        this._program.initialize([vert, frag], false);

        this._aMeshVertex = this._program.attribute('a_vertex', 0);
        this._aMeshTexCoord = this._program.attribute('a_texCoord', 1);
        this._program.link();

        this._uViewProjection = this._program.uniform('u_viewProjection');

protected onInitialize(context: Context, callback: Invalidate,
        mouseEventProvider: MouseEventProvider,
        /* keyEventProvider: KeyEventProvider, */
        /* touchEventProvider: TouchEventProvider */): boolean {

        context.enable(['ANGLE_instanced_arrays', 'OES_standard_derivatives',
            'WEBGL_color_buffer_float', 'OES_texture_float', 'OES_texture_float_linear']);

        this._defaultFBO = new DefaultFramebuffer(context, 'DefaultFBO');
        this._defaultFBO.initialize();
        this._defaultFBO.bind();

        const gl = context.gl as WebGLRenderingContext;
        const gl2facade = this._context.gl2facade;

        this._cuboids = new Array(4);
        for (let i = 0; i < this._cuboids.length; ++i) {
            this._cuboids[i] = new CuboidGeometry(context, 'cube', true, [0.25, 0.5 + 0.5 * i, 2.0]);
            this._cuboids[i].initialize();
        }

        this._plane = new PlaneGeometry(context, 'plane');
        this._plane.initialize();
        this._plane.scale = vec2.fromValues(100, 100);

protected onInitialize(context: Context, callback: Invalidate,
        /* mouseEventProvider: MouseEventProvider, */
        /* keyEventProvider: KeyEventProvider, */
        /* touchEventProvider: TouchEventProvider */): boolean {

        /* Create framebuffers, textures, and render buffers. */

        this._defaultFBO = new DefaultFramebuffer(this._context, 'DefaultFBO');
        this._defaultFBO.initialize();

        /* Create and configure test navigation. */

        this._camera = new Camera();

        /* Create and configure label pass. */

        this._labelPass = new LabelRenderPass(context);
        this._labelPass.initialize();
        this._labelPass.camera = this._camera;
        this._labelPass.target = this._defaultFBO;
        this._labelPass.depthMask = false;

        FontFace.fromFile('./data/opensans2048p160d16.fnt', context)
            .then((fontFace) => {

protected onInitialize(context: Context,
        callback: Invalidate,
        mouseEventProvider: MouseEventProvider | undefined): boolean {

        if (mouseEventProvider === undefined) {
            auxiliaries.log(auxiliaries.LogLevel.Error, 'MouseEventProvider was not supplied.');
            return false;
        }

        this._defaultFBO = new DefaultFramebuffer(this._context, 'DefaultFBO');
        this._defaultFBO.initialize();
        this._defaultFBO.bind();

        const gl = this._context.gl;

        this._ndcTriangle = new NdcFillingTriangle(this._context, 'NdcFillingTriangle');
        this._ndcTriangle.initialize();

        this.fetchTextures();

        // Initialize program and uniforms
        const vert = new Shader(this._context, gl.VERTEX_SHADER, 'ndcvertices');
        vert.initialize(require('./data/env-projections.vert'));

        const frag = new Shader(this._context, gl.FRAGMENT_SHADER, 'env-projections');
        frag.initialize(require('./data/env-projections.frag'));

protected onInitialize(context: Context, callback: Invalidate,
        /* mouseEventProvider: MouseEventProvider, */
        /* keyEventProvider: KeyEventProvider, */
        /* touchEventProvider: TouchEventProvider */): boolean {

        /* Create framebuffers, textures, and render buffers. */

        this._defaultFBO = new DefaultFramebuffer(this._context, 'DefaultFBO');
        this._defaultFBO.initialize();
        this._defaultFBO.bind();

        /* Create and configure canvas-size test pattern pass. */

        const gl = this._context.gl;

        this._ndcTriangle = new NdcFillingTriangle(this._context, 'NdcFillingTriangle');
        this._ndcTriangle.initialize();

        const vert = new Shader(this._context, gl.VERTEX_SHADER, 'ndcvertices (in-line)');
        vert.initialize(CanvasSizeRenderer.SHADER_SOURCE_VERT);
        const frag = new Shader(this._context, gl.FRAGMENT_SHADER, 'pattern (in-line)');
        frag.initialize(CanvasSizeRenderer.SHADER_SOURCE_FRAG);

        this._program = new Program(this._context, 'CanvasSizeProgram');

protected onInitialize(context: Context, callback: Invalidate,
        mouseEventProvider: MouseEventProvider,
        /* keyEventProvider: KeyEventProvider, */
        /* touchEventProvider: TouchEventProvider */): boolean {

        this._defaultFBO = new DefaultFramebuffer(context, 'DefaultFBO');
        this._defaultFBO.initialize();
        this._defaultFBO.bind();

        const gl = context.gl;


        this._cuboid = new CuboidGeometry(context, 'Cuboid', true, [2.0, 2.0, 2.0]);
        this._cuboid.initialize();


        const vert = new Shader(context, gl.VERTEX_SHADER, 'mesh.vert');
        vert.initialize(require('./data/mesh.vert'));
        const frag = new Shader(context, gl.FRAGMENT_SHADER, 'mesh.frag');
        frag.initialize(require('./data/mesh.frag'));

this._colorsImage.data(this.encodeFloatArray(colors));
            }

            this._verticesImage.wrap(gl.CLAMP_TO_EDGE, gl.CLAMP_TO_EDGE);
            this._verticesImage.filter(gl.NEAREST, gl.NEAREST);

            this._indicesImage.wrap(gl.CLAMP_TO_EDGE, gl.CLAMP_TO_EDGE);
            this._indicesImage.filter(gl.NEAREST, gl.NEAREST);

            this._colorsImage.wrap(gl.CLAMP_TO_EDGE, gl.CLAMP_TO_EDGE);
            this._colorsImage.filter(gl.NEAREST, gl.NEAREST);
        }

        this._uNdcOffset = this._program.uniform('u_ndcOffset');

        this._defaultFBO = new DefaultFramebuffer(this._context, 'DefaultFBO');
        this._defaultFBO.initialize();
        this._colorRenderTexture = new Texture2D(this._context, 'ColorRenderTexture');
        this._depthRenderbuffer = new Renderbuffer(this._context, 'DepthRenderbuffer');
        this._intermediateFBO = new Framebuffer(this._context, 'IntermediateFBO');

        this._accumulate = new AccumulatePass(this._context);
        this._accumulate.initialize(this._ndcTriangle);
        this._accumulate.precision = this._framePrecision;
        this._accumulate.texture = this._colorRenderTexture;

        this._blit = new BlitPass(this._context);
        this._blit.initialize(this._ndcTriangle);
        this._blit.readBuffer = gl2facade.COLOR_ATTACHMENT0;
        this._blit.drawBuffer = gl.BACK;
        this._blit.target = this._defaultFBO;