code: function getEventSourceArnRegions(event) {
    return event && event.Records ?
      event.Records.map(record => record.eventSourceARN ? getArnRegion(record.eventSourceARN) : '') : [];
  }
docs: Extracts the regions from the given event's record's eventSourceARN properties (if any); otherwise returns an empty
  array.
  
  Note that for this to work the given event should have records with an eventSourceARN property, which is the case for
  AWS Kinesis and DynamoDB stream events.
  
  @param event the event from which to extract its records' event source ARN regions
  @returns {string[]} the event's records' event source ARN regions (if any) or an empty array