Convert Two Flat Recordset to One Nested Recordset Using createMultipleContextCopies

The objective is to convert 2 different recordsets(SINGER and SONG) under same message, to single nested recordset (SONG nested under SINGER).
The message type:

The mapping:
For node SINGER, SINGERID and FULLNAME, is direct one-to-one mapping.
For node SONG and SONGNAME, please see below. The idea is for each SINGER, compare all SONG, if the SONG’s SINGERID is match, then map to target. Due to the list of SONG need to be compared as many as the SINGER count (6), so need to use function createMultipleContextCopies to create multiple copies of SONG list.

The queues:

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