Pamhyr2: Model: Add data traversal method on each pamhyr object.

src/Model/Pollutants/Pollutants.py

@@ -441,6 +441,16 @@ class Pollutants(SQLSubModel):
 
         return ok
 
+    def _data_traversal(self,
+                        predicate=lambda obj, data: True,
+                        modifier=lambda obj, data: None,
+                        data={}):
+        if predicate(self, data):
+            modifier(self, data)
+
+        for d in self._data:
+            d._data_traversal(predicate, modifier, data)
+
     @property
     def enabled(self):
         return self._enabled