How to use the regexpp.parseRegExpLiteral function in regexpp

function parseRegExp(node) {
            const evaluated = eslint_utils_1.getStaticValue(node, globalScope);
            if (evaluated == null || !(evaluated.value instanceof RegExp)) {
                return null;
            }
            const { pattern, flags } = regexpp_1.parseRegExpLiteral(evaluated.value);
            if (pattern.alternatives.length !== 1 ||
                flags.ignoreCase ||
                flags.global) {
                return null;
            }
            // Check if it can determine a unique string.
            const chars = pattern.alternatives[0].elements;
            if (!chars.every(c => c.type === 'Character')) {
                return null;
            }
            // To string.
            return String.fromCodePoint(...chars.map(c => c.value));
        }
        return {

function parseRegExp(node: TSESTree.Node): string | null {
      const evaluated = getStaticValue(node, globalScope);
      if (evaluated == null || !(evaluated.value instanceof RegExp)) {
        return null;
      }

      const { pattern, flags } = parseRegExpLiteral(evaluated.value);
      if (
        pattern.alternatives.length !== 1 ||
        flags.ignoreCase ||
        flags.global
      ) {
        return null;
      }

      // Check if it can determine a unique string.
      const chars = pattern.alternatives[0].elements;
      if (!chars.every(c => c.type === 'Character')) {
        return null;
      }

      // To string.
      return String.fromCodePoint(

const findLowercaseEscape = value => {
	const ast = parseRegExpLiteral(value);

	let escapeNodePosition;
	visitRegExpAST(ast, {
		/**
Record escaped node position in regexpp ASTNode. Returns undefined if not found.
@param {ASTNode} node A regexpp ASTNode. Note that it is of different type to the ASTNode of ESLint parsers
@returns {undefined}
*/
		onCharacterLeave(node) {
			if (escapeNodePosition) {
				return;
			}

			const matches = node.raw.match(escapePatternWithLowercase);

			if (matches && matches[2].slice(1).match(hasLowercaseCharacter)) {