With PartitionMapping's can I just get some clarification on what 'Overriding PartitionMapping outside of Dagster is not supported' means? does this mean, please don't implement your own partitionmapping class?

Hi Harrison. Partition mapping method signatures can change depending on internal callsites, so if you did implement your own partition mapping, it's possible that upgrading can lead to unexpected breakages if we changed the method signatures. If you don't mind this happening, you can implement your own partition mapping class. Another option is also opening up a PR to add your partition mapping to the dagster library, and we'll maintain it from there.

thanks. I'm use to my code breaking all the time, so that's not the biggest of issues 🙂