Refactor code structure and remove redundant changes

backend/apps/api/v1/serializers_rankings.py

@@ -4,8 +4,7 @@ API serializers for the ride ranking system.
 
 from rest_framework import serializers
 from drf_spectacular.utils import extend_schema_serializer, OpenApiExample
-
-from apps.rides.models import RideRanking, RidePairComparison, RankingSnapshot
+from django.utils.functional import cached_property
 
 
 @extend_schema_serializer(
@@ -45,8 +44,19 @@ class RideRankingSerializer(serializers.ModelSerializer):
     rank_change = serializers.SerializerMethodField()
     previous_rank = serializers.SerializerMethodField()
 
+    @cached_property
+    def _model(self):
+        from apps.rides.models import RideRanking
+
+        return RideRanking
+
     class Meta:
-        model = RideRanking
+        @property
+        def model(self):
+            from apps.rides.models import RideRanking
+
+            return RideRanking
+
         fields = [
             "id",
             "rank",
@@ -79,6 +89,8 @@ class RideRankingSerializer(serializers.ModelSerializer):
 
     def get_rank_change(self, obj):
         """Calculate rank change from previous snapshot."""
+        from apps.rides.models import RankingSnapshot
+
         latest_snapshots = RankingSnapshot.objects.filter(ride=obj.ride).order_by(
             "-snapshot_date"
         )[:2]
@@ -89,6 +101,8 @@ class RideRankingSerializer(serializers.ModelSerializer):
 
     def get_previous_rank(self, obj):
         """Get previous rank."""
+        from apps.rides.models import RankingSnapshot
+
         latest_snapshots = RankingSnapshot.objects.filter(ride=obj.ride).order_by(
             "-snapshot_date"
         )[:2]
@@ -106,7 +120,7 @@ class RideRankingDetailSerializer(serializers.ModelSerializer):
     ranking_history = serializers.SerializerMethodField()
 
     class Meta:
-        model = RideRanking
+        model = "rides.RideRanking"
         fields = [
             "id",
             "rank",
@@ -167,6 +181,7 @@ class RideRankingDetailSerializer(serializers.ModelSerializer):
     def get_head_to_head_comparisons(self, obj):
         """Get top head-to-head comparisons."""
         from django.db.models import Q
+        from apps.rides.models import RidePairComparison
 
         comparisons = (
             RidePairComparison.objects.filter(Q(ride_a=obj.ride) | Q(ride_b=obj.ride))
@@ -207,6 +222,8 @@ class RideRankingDetailSerializer(serializers.ModelSerializer):
 
     def get_ranking_history(self, obj):
         """Get recent ranking history."""
+        from apps.rides.models import RankingSnapshot
+
         history = RankingSnapshot.objects.filter(ride=obj.ride).order_by(
             "-snapshot_date"
         )[:30]
@@ -228,7 +245,7 @@ class RankingSnapshotSerializer(serializers.ModelSerializer):
     park_name = serializers.CharField(source="ride.park.name", read_only=True)
 
     class Meta:
-        model = RankingSnapshot
+        model = "rides.RankingSnapshot"
         fields = [
             "id",
             "ride",