Originally these functions were rejected for inclusion to puppetlab's stdlib. Now equivalent functions have been added there making these unnecessary.
This has been moved to voxpupuli's extlib starting with v6.2.0 released February 28 2023
There is a to_json and a to_json_pretty function in puppetlab's stdlib
starting with version 4.20.0 released September 11
2017
There is a join_keys_to_values function in puppetlab's
stdlib that has been there
since
2012.
There is no equivalent I've found.
There is a to_yaml function in puppetlab's
stdlib starting with version
4.20.0 released September 11
2017