How to use the postcss-values-parser function in postcss-values-parser

export default function transpileDecl(result, promises, decl, opts, cache) { // eslint-disable-line max-params
	// path to the current working file and directory by declaration
	const declWF = path.resolve(decl.source && decl.source.input && decl.source.input.file ? decl.source.input.file : result.root.source && result.root.source.input && result.root.source.input.file ? result.root.source.input.file : path.join(process.cwd(), 'index.css'));
	const declWD = path.dirname(declWF);

	// list of files to watch
	const files = {};

	// walk each node of the declaration
	const declAST = parser(decl.value).parse();

	declAST.walk(node => {
		// if the node is a url containing an svg fragment
		if (isExternalURLFunction(node)) {
			//  of url()
			const urlNode = node.nodes[1];

			//  split by fragment identifier symbol (#)
			const urlParts = urlNode.value.split('#');

			//  src
			const src = urlParts[0];

			//  fragment identifier
			const id = urlParts.slice(1).join('#');

styleAST.walkDecls(decl => {
		const declAST = parser(decl.value).parse();

		// update the declaration with all transpiled var()s
		declAST.walk(node => {
			// conditionally update the var()
			if (isVarFuntion(node)) {
				transpileVar(node, params);
			}
		});

		decl.value = declAST.toString();
	});

css.walkDecls(decl => {
            const valueAst = parser(decl.value).parse();

            valueAst.walk(child => {
                if (child.type !== 'operator' || (child.value !== '+' && child.value !== '-')) {
                    return;
                }

                const {parent} = child;

                // 当前 child 的索引
                const index = parent.index(child);

                // child 的后一个元素
                const nextElem = parent.nodes[index + 1];

                // child 的前一个元素
                const prevElem = parent.nodes[index - 1] || {};

css.walkDecls(decl => {
            const valueAst = parser(decl.value).parse();

            valueAst.walk(child => {
                if (child.type !== 'operator') {
                    return;
                }

                const {parent} = child;

                // 当前 child 的索引
                const index = parent.index(child);

                // child 的后一个元素
                const nextElem = parent.nodes[index + 1];

                // child 的前一个元素
                const prevElem = parent.nodes[index - 1];

root.walkDecls(decl => {
			if (hasAlphaHex(decl)) {
				// replace instances of hexa with rgba()
				const ast = valueParser(decl.value).parse();

				walk(ast, node => {
					if (isAlphaHex(node)) {
						node.replaceWith(hexa2rgba(node));
					}
				});

				// conditionally update the declaration
				const modifiedValue = String(ast);

				if (decl.value !== modifiedValue) {
					if (preserve) {
						decl.cloneBefore({ value: modifiedValue });
					} else {
						decl.value = modifiedValue;
					}

root.walkDecls(decl => {
		if (hasGrayFunction(decl)) {
			const { value: originalValue } = decl;

			// parse the declaration value
			const ast = parser(originalValue).parse();

			// walk every node in the value that contains a gray() function
			ast.walk(node => {
				const [lightness, alpha] = getFunctionGrayArgs(node);

				if (lightness !== undefined) {
					// rename the gray() function to rgb()
					node.value = 'rgb';

					// convert the lab gray lightness into rgb
					const [r, g, b] = lab2rgb(lightness, 0, 0).map(
						channel => Math.max(Math.min(Math.round(channel * 2.55), 255), 0)
					);

					// preserve the slash nodes within rgb()
					const openingSlash = node.first;

root.walkDecls(decl => {
			const originalValue = decl.value;

			if (colorModFunctionMatch.test(originalValue)) {
				const ast = parser(originalValue, { loose: true }).parse();

				transformAST(ast, {
					unresolved: unresolvedOpt,
					stringifier: stringifierOpt,
					transformVars: transformVarsOpt,
					decl,
					result,
					customProperties
				});

				const modifiedValue = ast.toString();

				if (originalValue !== modifiedValue) {
					decl.value = modifiedValue;
				}
			}

function importCustomPropertiesFromObject(object) {
	const customProperties = Object.assign(
		{},
		Object(object).customProperties || Object(object)['custom-properties']
	);

	for (const prop in customProperties) {
		customProperties[prop] = valueParser(customProperties[prop]).parse();
	}

	return customProperties;
}