code: function parseLocalData(fileObj, options, extendedData = {}) {
    fileObj.data = fileObj.data || {};
    for (const dataKey in fileObj.data) {
      const parsedField = parseField(dataKey, fileObj.data[dataKey], options);
      fileObj.data[dataKey] = parsedField.contents;
    }
    Object.assign(fileObj, extendedData);
    return fileObj;
  }
docs: Given an object representing a page or pattern or other file:
  If that object has a `data` property, use that to
  create the right kind of context for the object. Parse field data with
  any indicated parsers.
  @TODO is `extendedData` used by any callers?