Gtk.TreeViewColumn.prototype.pack_start

function pack_start(cell:Gtk.CellRenderer, expand:Boolean):void {
    // Gjs wrapper for gtk_tree_view_column_pack_start()
}

Packs the cell into the beginning of the column. If expand is false, then the cell is allocated no more space than it needs. Any unused space is divided evenly between cells for which expand is true.