Grid-Band: How to set a Grid Band initially expanded thought Code Snippet?

I group by default the Open Approvals through following Code Snippet (posted by One Identity in its documentation).

var dataSource = GridBand1.DataSource;

var col = dataSource.Table.GetColumn("My Column");
if (!dataSource.GroupingColumns.Contains(col))

By using this script, the information is initially grouped by this colummn but also compressed.
I would like to have it also expanded.

Any ideas?
Thank you in advance!