docs: function resolveVariable (match, record) {
      // return empty string if no record
      if (!defined(record)) {
          return ''
      }
      // remove ${} from variable
      match = match.substr(2, match.length - 3)
      // try to get value from record
      var value = _.get(record, match)
      // try to get value from data if not found
      if (!defined(value)) {
          value = _.get(record.data, match)
      }
      // return value or empty string
      return defined(value) ? value : ''
  }