tests: fix test for breaking pydantic v2.12 change

Fixes a test failure introduced by
pydantic/pydantic#11957

TL;DR: "after" model validators should be instance methods, not class
methods. Batch model updated to use an instance method, which fixes the
failing test.

Author: psychedelicious

invokeai/app/services/session_queue/session_queue_common.py

@@ -1,7 +1,7 @@
 import datetime
 import json
 from itertools import chain, product
-from typing import Generator, Literal, Optional, TypeAlias, Union, cast
+from typing import Generator, Literal, Optional, TypeAlias, Union
 
 from pydantic import (
     AliasChoices,
@@ -15,7 +15,6 @@
 )
 from pydantic_core import to_jsonable_python
 
-from invokeai.app.invocations.baseinvocation import BaseInvocation
 from invokeai.app.invocations.fields import ImageField
 from invokeai.app.services.shared.graph import Graph, GraphExecutionState, NodeNotFoundError
 from invokeai.app.services.workflow_records.workflow_records_common import (
@@ -137,20 +136,18 @@ def validate_unique_field_mappings(cls, v: Optional[BatchDataCollection]):
         return v
 
     @model_validator(mode="after")
-    def validate_batch_nodes_and_edges(cls, values):
-        batch_data_collection = cast(Optional[BatchDataCollection], values.data)
-        if batch_data_collection is None:
-            return values
-        graph = cast(Graph, values.graph)
-        for batch_data_list in batch_data_collection:
+    def validate_batch_nodes_and_edges(self):
+        if self.data is None:
+            return self
+        for batch_data_list in self.data:
             for batch_data in batch_data_list:
                 try:
-                    node = cast(BaseInvocation, graph.get_node(batch_data.node_path))
+                    node = self.graph.get_node(batch_data.node_path)
                 except NodeNotFoundError:
                     raise NodeNotFoundError(f"Node {batch_data.node_path} not found in graph")
                 if batch_data.field_name not in type(node).model_fields:
                     raise NodeNotFoundError(f"Field {batch_data.field_name} not found in node {batch_data.node_path}")
-        return values
+        return self
 
     @field_validator("graph")
     def validate_graph(cls, v: Graph):