Don't overwrite user defined model_function

Author: smlindauer

src/sasctl/pzmm/write_json_files.py

@@ -351,17 +351,17 @@ def write_model_properties_json(
                 )
 
         if not target_values:
-            model_function = "Prediction"
+            model_function = model_function if model_function else "Prediction"
             target_level = "INTERVAL"
             target_event = ""
             event_prob_var = ""
         elif isinstance(target_values, list) and len(target_values) == 2:
-            model_function = "Classification"
+            model_function = model_function if model_function else "Classification"
             target_level = "BINARY"
             target_event = str(target_values[0])
             event_prob_var = f"P_{target_values[0]}"
         elif isinstance(target_values, list) and len(target_values) > 2:
-            model_function = "Classification"
+            model_function = model_function if model_function else "Classification"
             target_level = "NOMINAL"
             target_event = ""
             event_prob_var = ""