fix: modified write_yaml method in parameter_node.py to output th…

…e node data as a YAML file

WIP

fixes: PolicyEngine#274

changelog_entry.yaml

@@ -0,0 +1,5 @@
+- bump: minor
+  changes:
+    added:
+    - `write_yaml` function to output ParameterNode data to a YAML file
+    - `test_write_yaml` test to produce a sample output

policyengine_core/parameters/parameter_node.py

@@ -278,13 +278,15 @@ def get_child(self, path: str) -> "ParameterNode":
         return node
 
     def write_yaml(self, file_path: Path) -> yaml:
-        data = {"description": self.description}
+        data = {"name": self.name, "description": self.description}
         for key, value in self.children.items():
             name = key
-            value_at_instant = value.values_list[0]
-            data[name] = {"values": {value_at_instant.instant_str: value_at_instant.value}}
+            value_dict = {}
+            data[name] = {"values": value_dict}
+            for value_at_instant in value.values_list:
+                value_dict[value_at_instant.instant_str] = value_at_instant.value
         try:
             with open(file_path, "w") as f:
-                yaml.dump(data, f)
+                yaml.dump(data, f, sort_keys=False)
         except Exception as e:
             print(f"Error when writing YAML file: {e}")

tests/core/test_parameters.py

@@ -145,9 +145,19 @@ def test_name():
 
 
 def test_write_yaml():
-    parameter_data = {
-        "description": "Parameter indexed by a numeric key",
-        "2010": {"values": {"2006-01-01": 0.0075}},
+    parameter_data={
+        'amount': {
+            'values': {
+                "2015-01-01": {'value': 550},
+                "2016-01-01": {'value': 600}
+            }
+        },
+        'min_age': {
+            'values': {
+                "2015-01-01": {'value': 25},
+                "2016-01-01": {'value': 18}
+            }
+        },
     }
     parameter = ParameterNode("root", data=parameter_data)
     parameter.write_yaml(Path("output.yaml"))