Remove inferred is_parent formula (#1595)

Author: MaxGhenis

changelog.d/1031.md

@@ -0,0 +1 @@
+Removed the inferred `is_parent` formula so datasets provide parent status directly.

policyengine_uk/tests/policy/baseline/household/demographic/is_parent.yaml

@@ -0,0 +1,34 @@
+- name: is_parent is not inferred from family composition
+  period: 2024
+  input:
+    people:
+      adult:
+        age: 35
+      child:
+        age: 5
+    benunits:
+      benunit:
+        members: [adult, child]
+    households:
+      household:
+        members: [adult, child]
+  output:
+    is_parent: [false, false]
+
+- name: is_parent can be provided as an input
+  period: 2024
+  input:
+    people:
+      adult:
+        age: 35
+        is_parent: true
+      child:
+        age: 5
+    benunits:
+      benunit:
+        members: [adult, child]
+    households:
+      household:
+        members: [adult, child]
+  output:
+    is_parent: [true, false]

policyengine_uk/variables/household/demographic/is_parent.py

@@ -6,25 +6,4 @@ class is_parent(Variable):
     entity = Person
     label = "Whether this person is a parent in their benefit unit"
     definition_period = YEAR
-
-    def formula(person, period, parameters):
-        benunit = person.benunit
-        age = person("age", period)
-        family_type = benunit("family_type", period)
-
-        # Find two oldest members
-        benunit_ages = benunit.members("age", period)
-        adult_index = person("adult_index", period)
-
-        # Get family types enum
-        family_types = family_type.possible_values
-
-        # For lone parents (FamilyType.LONE_PARENT), only the eldest is parent
-        is_lone_parent = (family_type == family_types.LONE_PARENT) & (adult_index == 1)
-
-        # For couples with children (FamilyType.COUPLE_WITH_CHILDREN), two eldest are parents
-        is_couple_parent = (family_type == family_types.COUPLE_WITH_CHILDREN) & (
-            (adult_index == 1) | (adult_index == 2)
-        )
-
-        return is_lone_parent | is_couple_parent
+    default_value = False