Update pyiceberg/expressions/__init__.py

Co-authored-by: Fokko Driesprong <fokko@apache.org>

Author: Aniketsy

pyiceberg/expressions/__init__.py

@@ -562,7 +562,7 @@ def as_bound(self) -> Type[BoundNotNaN[L]]:
 
 
 class SetPredicate(UnboundPredicate[L], IcebergBaseModel, ABC):
-    type: str = Field(default="in", alias="type")
+    type: TypingLiteral["in", "not-in"] = Field(default="in", alias="type")
     literals: Set[Literal[L]] = Field(alias="items")
 
     def __init__(self, term: Union[str, UnboundTerm[Any]], literals: Union[Iterable[L], Iterable[Literal[L]]]):