Fix pydantic validator

nomenclature/code.py

@@ -3,20 +3,21 @@
 from keyword import iskeyword
 from pathlib import Path
 from typing import Any
+
+from pyam.utils import to_list
 from pydantic import (
-    field_validator,
-    field_serializer,
-    model_validator,
-    ConfigDict,
     BaseModel,
+    ConfigDict,
     Field,
     ValidationInfo,
+    field_serializer,
+    field_validator,
+    model_validator,
 )
+from typing_extensions import Self
 
 from nomenclature.error import ErrorCollector
 
-from pyam.utils import to_list
-
 from .countries import countries
 
 
@@ -210,11 +211,12 @@ def convert_none_to_empty_string(cls, v):
         return v if v is not None else ""
 
     @model_validator(mode="after")
-    def wildcard_must_skip_region_aggregation(cls, data):
-        if "*" in data.name and data.skip_region_aggregation is False:
+    def wildcard_must_skip_region_aggregation(self) -> Self:
+        if self.is_wildcard and self.skip_region_aggregation is False:
             raise ValueError(
-                f"Wildcard variable '{data.name}' must skip region aggregation"
+                f"Wildcard variable '{self.name}' must skip region aggregation"
             )
+        return self
 
     @field_validator("components", mode="before")
     def cast_variable_components_args(cls, v):
@@ -232,6 +234,10 @@ def cast_variable_components_args(cls, v):
     def convert_str_to_none_for_writing(self, v):
         return v if v != "" else None
 
+    @property
+    def is_wildcard(self) -> bool:
+        return "*" in self.name
+
     @property
     def units(self) -> list[str]:
         return self.unit if isinstance(self.unit, list) else [self.unit]