code: function getEventSources(event) {
    return event && Array.isArray(event.Records) ? event.Records.map(getEventSource) : [];
  }
docs: Returns the event sources of the given stream event's records (if any); otherwise returns an empty array.
  @param {AnyStreamEvent|*} event - a Kinesis or DynamoDB stream event
  @returns {string[]} an array of event sources (one for each stream event record)