How do I merge two .rrd files?

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Python

I have a set of rrd files of which I'd like to merge two rrd files? I have been trying to achieve this for a while with no success. There seem to be python scripts online for combining rrd files, but they all appear to be outdated. Please do let me know if anyone has any idea of how to combine them or if anyone has an updated script. Thanks

What I have tried:

I have tried using python scripts that are found online that use rrdtools for merging two or more rrd files, but the scripts appear to be outdated.