This example loads the classic Iris flower dataset from a CSV file and displays the average sepal length for each of the three species as a formatted JSON summary. It demonstrates loading data asynchronously via `fetch`, parsing it with `csvParse`, and converting string values to numbers. The code uses `flatRollup` and `sum` from D3 v7 to aggregate the data, then renders the result as plain text in a `<pre>` element.