code: 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;
    };
  }
docs: Returns the transformer which acts on the MDAST tree and given VFile.
  
  If `options.simple` is passed as a truthy value, the plugin will convert
  to `<div class="mermaid">` rather than a SVG image.
  
  @link https://github.com/unifiedjs/unified#function-transformernode-file-next
  @link https://github.com/syntax-tree/mdast
  @link https://github.com/vfile/vfile
  
  @param {object} options
  @return {function}