function-orchestrator code can be found at https://gerrit.wikimedia.org/g/mediawiki/services/function-orchestrator
Look for this task's ID in src/builtins.js
Currently, these functions work with a Z10 of Z22s, which has to change because 1) Z10 should be a generic list (Z10 is deprecated) and 2) Z22s should be generic Pairs (Z22 is now the result envelope type).
A List of Pairs is just a Map.