docs: function mermaid(options = {}) {
    const simpleMode = options.simple || false;
  
    /**
     * @param {object} ast MDAST
     * @param {vFile} vFile
     * @param {function} next
     * @return {object}
     */
    return function transformer(ast, vFile, next) {
      visitCodeBlock(ast, vFile, simpleMode);
      visitLink(ast, vFile, simpleMode);
      visitImage(ast, vFile, simpleMode);
  
      if (typeof next === 'function') {
        return next(null, ast, vFile);
      }
  
      return ast;
    };
  }