Can healpix_29/hipscat_index be non-unique

[nevencaplar]

Investigate if there is anything that will break if healpix_29/hipscat_index is not a unique number, with a particular focus on pandas/DASK. One way to approach this would be to create a dataset with explicit healpix_29/hipscat_index that repeats and conduct a small analysis (e.g., periodogram) and see if there are failures.