Update api.py

src/curies/api.py

@@ -36,7 +36,8 @@
 from pydantic import BaseModel, Field
 from pytrie import StringTrie
 
-from ._pydantic_compat import field_validator, get_field_validator_values, PYDANTIC_V1
+from ._pydantic_compat import PYDANTIC_V1, field_validator, get_field_validator_values
+
 if not PYDANTIC_V1:
     from pydantic import ConfigDict
 
@@ -204,13 +205,15 @@ class notion of parsed reference (instead of merely stringified
     )
 
     if PYDANTIC_V1:
+
         class Config:
             """Pydantic configuration for references."""
+
             frozen = True
+
     else:
         model_config = ConfigDict(frozen=True)
 
-
     @property
     def curie(self) -> str:
         """Get the reference as a CURIE string.