Submit an asynchronous export job for this account's ETF data. dataset selects the source: metrics (default), countries, sectors, or holdings. Choose symbols and/or isins and a from/to window (metrics also accepts a metric-name list); a batch worker materialises the Parquet export, then poll GET /etfs/exports/{exportId} for signed download links. symbols and isins union; omit both for the full universe. Scoped to the caller's API key.