toArray(columnName) {
        return columnName
            ? Array.from(this).map((row) => row.get(columnName))
            : Array.from(this).map((row) => row.toArray());
    }
Convert DataFrame into Array of Arrays. You can also extract only one column as Array.
@param {String} [columnName] Column Name to extract. By default, all columns are transformed.
@returns {Array} The DataFrame (or the column) converted into Array.
@example
df.toArray()