code: function normalizeFields (options) {
    const fields = options.fields || options.outFields
    const idField = _.get(options, 'collection.metadata.idField')
    if (options.returnIdsOnly === true && idField) return [idField]
    else if (options.returnIdsOnly === true) return ['OBJECTID']
    if (fields === '*') return undefined
    if (typeof fields === 'string' || fields instanceof String) return fields.split(',')
    if (fields instanceof Array) return fields
    return undefined
  }
docs: Transform the input of requested response fields
  @param {Object} options - object that may contain 'fields' or 'outFields' property