update unions serializer to get around pyright issue

Author: iscai-msft

packages/http-client-python/generator/pygen/codegen/models/model_type.py

@@ -77,10 +77,9 @@ def __init__(
         self.cross_language_definition_id: Optional[str] = self.yaml_data.get("crossLanguageDefinitionId")
         self.usage: int = self.yaml_data.get("usage", UsageFlags.Input.value | UsageFlags.Output.value)
         self.client_namespace: str = self.yaml_data.get("clientNamespace", code_model.namespace)
-        self.is_typed_dict_only: bool = (
-            self.yaml_data.get("typedDictOnly", False)
-            or self.name in code_model.options.get("typed-dict-only-models", [])
-        )
+        self.is_typed_dict_only: bool = self.yaml_data.get(
+            "typedDictOnly", False
+        ) or self.name in code_model.options.get("typed-dict-only-models", [])
 
     @property
     def is_usage_output(self) -> bool:
@@ -396,8 +395,7 @@ def imports(self, **kwargs: Any) -> FileImport:
                     ImportType.LOCAL,
                 )
             elif serialize_namespace_type in [NamespaceType.TYPES_FILE, NamespaceType.UNIONS_FILE] or (
-                serialize_namespace_type == NamespaceType.MODEL
-                and kwargs.get("called_by_property", False)
+                serialize_namespace_type == NamespaceType.MODEL and kwargs.get("called_by_property", False)
             ):
                 file_import.add_submodule_import(
                     relative_path,

packages/http-client-python/generator/pygen/codegen/serializers/unions_serializer.py

@@ -43,11 +43,19 @@ def imports(self) -> FileImport:
                     serialize_namespace_type=NamespaceType.UNIONS_FILE,
                 )
             )
+        for model in self.discriminated_base_models:
+            for subtype in model.discriminated_subtypes.values():
+                file_import.merge(
+                    subtype.imports(
+                        serialize_namespace=self.serialize_namespace,
+                        serialize_namespace_type=NamespaceType.UNIONS_FILE,
+                    )
+                )
         return file_import
 
     def discriminated_subtypes_union(self, model: ModelType) -> str:
         subtypes = list(model.discriminated_subtypes.values())
-        subtype_names = [s.name for s in subtypes]
+        subtype_names = [s.type_annotation(skip_quote=True) for s in subtypes]
         return f"{model.name} = Union[{', '.join(subtype_names)}]"
 
     def serialize(self) -> str: