This example demonstrates how to clean, group, and enrich SPARQL query results about ethnographic artefacts. It loads data from a Dutch heritage endpoint using `d3.json`, maps each row to extract plain values with `cleanData`, then applies `d3.nest()` to group artefacts by their parent country. For each country group, it calculates the total count of artefacts as a new `amount` property. The code uses d3 v5 APIs such as `d3.nest()` and `d3.json`, and logs the raw, cleaned, and transformed data to the console for inspection.