Add Basic Database functions.

dsst/dsst_gtk3/util.py

@@ -0,0 +1,9 @@
+class Util:
+    @staticmethod
+    def get_combo_value(combo, index: int):
+        """ Retrieve the selected value of a combo box at the selected index in the model """
+        tree_iter = combo.get_active_iter()
+        if tree_iter:
+            return combo.get_model().get_value(tree_iter, index)
+        else:
+            return None