function getSpecialAttributes(node) {
            var specialAttributes = []
            var value = node.attrs['id']
            if (value) {
                specialAttributes.push(`#${value}`)
            }
            value = node.attrs['class']
            if (value) {
                specialAttributes.push(value.split(/\s+/).map(function (klass) {
                    return `.${klass}`
                }).join(' '))
            }
            Object.keys(node.attrs).forEach(function (key) {
                if (ignoreAttributes.indexOf(key) == -1) {
                    specialAttributes.push(`${key}=${value}`)
                }
            })
            specialAttributes = specialAttributes.join(' ')

            if (specialAttributes.length <= 0) {
                return ''
            } else {
                return ` (${specialAttributes})`
            }
        }
implement based on https://michelf.ca/projects/php-markdown/extra/