How to use the @pixi/constants.ENV.WEBGL_LEGACY function in @pixi/constants

contextChange()
    {
        const gl = this.renderer.gl;

        if (settings.PREFER_ENV === ENV.WEBGL_LEGACY)
        {
            this.MAX_TEXTURES = 1;
        }
        else
        {
            // step 1: first check max textures the GPU can handle.
            this.MAX_TEXTURES = Math.min(
                gl.getParameter(gl.MAX_TEXTURE_IMAGE_UNITS),
                settings.SPRITE_MAX_TEXTURES);

            // step 2: check the maximum number of if statements the shader can have too..
            this.MAX_TEXTURES = checkMaxIfStatementsInShader(
                this.MAX_TEXTURES, gl);
        }

        this._shader = this.shaderGenerator.generateShader(this.MAX_TEXTURES);

this.CONTEXT_UID = this.renderer.CONTEXT_UID;
        this.current = this.unknownFramebuffer;
        this.viewport = new Rectangle();
        this.hasMRT = true;
        this.writeDepthTexture = true;

        this.disposeAll(true);

        // webgl2
        if (this.renderer.context.webGLVersion === 1)
        {
            // webgl 1!
            let nativeDrawBuffersExtension = this.renderer.context.extensions.drawBuffers;
            let nativeDepthTextureExtension = this.renderer.context.extensions.depthTexture;

            if (settings.PREFER_ENV === ENV.WEBGL_LEGACY)
            {
                nativeDrawBuffersExtension = null;
                nativeDepthTextureExtension = null;
            }

            if (nativeDrawBuffersExtension)
            {
                gl.drawBuffers = (activeTextures) =>
                    nativeDrawBuffersExtension.drawBuffersWEBGL(activeTextures);
            }
            else
            {
                this.hasMRT = false;
                gl.drawBuffers = () =>
                {
                    // empty

contextChange()
    {
        const gl = this.renderer.gl;

        if (settings.PREFER_ENV === ENV.WEBGL_LEGACY)
        {
            this.MAX_TEXTURES = 1;
        }
        else
        {
            // step 1: first check max textures the GPU can handle.
            this.MAX_TEXTURES = Math.min(gl.getParameter(gl.MAX_TEXTURE_IMAGE_UNITS), settings.SPRITE_MAX_TEXTURES);

            // step 2: check the maximum number of if statements the shader can have too..
            this.MAX_TEXTURES = checkMaxIfStatementsInShader(this.MAX_TEXTURES, gl);
        }

        // generate generateMultiTextureProgram, may be a better move?
        this.shader = generateMultiTextureShader(gl, this.MAX_TEXTURES);

        // we use the second shader as the first one depending on your browser may omit aTextureId

contextChange()
    {
        this.disposeAll(true);

        const gl = this.gl = this.renderer.gl;
        const context = this.renderer.context;

        this.CONTEXT_UID = this.renderer.CONTEXT_UID;

        // webgl2
        if (!gl.createVertexArray)
        {
            // webgl 1!
            let nativeVaoExtension = this.renderer.context.extensions.vertexArrayObject;

            if (settings.PREFER_ENV === ENV.WEBGL_LEGACY)
            {
                nativeVaoExtension = null;
            }

            if (nativeVaoExtension)
            {
                gl.createVertexArray = () =>
                    nativeVaoExtension.createVertexArrayOES();

                gl.bindVertexArray = (vao) =>
                    nativeVaoExtension.bindVertexArrayOES(vao);

                gl.deleteVertexArray = (vao) =>
                    nativeVaoExtension.deleteVertexArrayOES(vao);
            }
            else

contextChange()
    {
        const gl = this.renderer.gl;

        if (settings.PREFER_ENV === ENV.WEBGL_LEGACY)
        {
            this.MAX_TEXTURES = 1;
        }
        else
        {
            // step 1: first check max textures the GPU can handle.
            this.MAX_TEXTURES = Math.min(
                gl.getParameter(gl.MAX_TEXTURE_IMAGE_UNITS),
                settings.SPRITE_MAX_TEXTURES);

            // step 2: check the maximum number of if statements the shader can have too..
            this.MAX_TEXTURES = checkMaxIfStatementsInShader(
                this.MAX_TEXTURES, gl);
        }

        this._shader = this.shaderGenerator.generateShader(this.MAX_TEXTURES);