auto sharding strategy for theta sketch

I was going through the pr : https://github.com/apache/pinot/pull/5316
Can you please point me to how or where is this implemented. How do we define high cardinality threshold

I am running into issues where different sets can be different cardinality and error is high and wanted insights on how to tune theta params during my indexing phase . what is a reasonable theta threshold to decide high cardinality

Start with pull request 5316 and trace how auto sharding for theta sketches is implemented. Document where the high-cardinality threshold is defined, how theta parameters affect indexing error, and what guidance is available for choosing a threshold across datasets with different cardinalities.

Written by the indexing model from the issue text.