src/utils/front-matter.js/print
function print(node, textToDoc) {
  if (node.lang === "yaml") {
    const value = node.value.trim();
    const doc = value
      ? textToDoc(value, { parser: "yaml" }, { stripTrailingHardline: true })
      : "";
    return markAsRoot(
      concat(["---", hardline, doc, doc ? hardline : "", "---"])
    );
  }
}