function defaultTitleAndKeylabel () {
  return function _defaultTitleAndKeylabel (metricInstances) {
    return metricInstances.map(mi => {
      const defaultTitle = (mi.instance === -1 || mi.instance === '-1') ? mi.metric : `${mi.metric} (${mi.instance})`
      return { ...mi, title: defaultTitle, keylabel: defaultTitle }
    })
  }
}
Adds a default title and keylabel to the metric instances

@return {function} a transform function