Minor linting improvements - see HEA-688

Author: rhunwicks

apps/common/lookups.py

@@ -9,6 +9,7 @@
 
 import pandas as pd
 from django.contrib.auth.models import User
+from django.db.models import Model
 
 from .fields import translation_fields
 from .models import (
@@ -31,7 +32,7 @@ class Lookup(ABC):
 
     # The primary key fields for the model being retrieved, typically
     # a single auto-incremented surrogate key named `id`
-    id_fields = None
+    id_fields = []
 
     # The fields passed from the dataframe that are used to constrain the lookup,
     # typically the fields that are foreign keys from the model being looked up to
@@ -346,7 +347,7 @@ def get(self, value: str, **parent_values) -> str | None:
             return None
 
     @functools.cache
-    def get_instance(self, value: str, **parent_values) -> str | None:
+    def get_instance(self, value: str, **parent_values) -> Model | None:
         """
         Return the Django model instance for a single string, or None if there is no match.
 

pipelines/assets/livelihood_activity.py

@@ -436,6 +436,11 @@ def get_instances_from_dataframe(
                     )
                 ]
 
+                # Assertion to prevent linting from complaining about possible None values
+                assert livelihood_strategy is not None, (
+                    "Found Livelihood Activities from row %s, but there is no Livelihood Strategy defined." % row
+                )
+
                 # Don't save Livelihood Strategies from the Data worksheet that are captured in more detail
                 # on the Data2 or Data3 worksheets. These strategies have entries in the Data sheet like 'Construction cash income -- see Data2'
                 if non_empty_livelihood_activities and re.match(