GET a collection of V2 and V3 API List IDs

<div class="Msg Msg--warning"><p class="note-text">Use this endpoint to migrate your locally stored V2 contact list data to the new V3 format. Developers are expected to use this endpoint sparingly. This endpoint is NOT intended for regular or repeated use. Constant Contact will eventually deprecate and remove this endpoint.</p></div>

This GET call retrieves a collection of cross-referenced list sequence IDs (id used in the V2 API) and UUIDs (list_id used in the V3 API). This endpoint is intended for developers who have an existing V2 API integration, and are migrating their users to a new V3 API integration. The V2 and V3 APIs use different resource ID formats. Use the sequence_ids query parameter to specify a set of comma delimited V2 list ids to cross-reference. See Migrating Apps and Data to V3 to learn more."

{
  "xrefs": [
    {
      "sequence_id": "0016633325",
      "list_id": "71600990-908b-11e6-907f-1200166bff25"
    }
  ]
}