code: function getDynamoDBEventSourceTableNames(event) {
    return event && Array.isArray(event.Records) ? event.Records.map(getDynamoDBEventSourceTableName) : [];
  }
docs: Extracts and returns the table names from the given DynamoDB stream event's records' eventSourceARNs (if any);
  otherwise returns an empty array.
  @param {DynamoDBEvent|*} event - a DynamoDB stream event
  @returns {string[]} an array of event source table names (one for each stream event record)