Make Not expression JSON serializable

Author: Aniketsy

pyiceberg/expressions/__init__.py

@@ -32,14 +32,16 @@
     Union,
 )
 
+from pydantic import model_validator
+
 from pyiceberg.expressions.literals import (
     AboveMax,
     BelowMin,
     Literal,
     literal,
 )
 from pyiceberg.schema import Accessor, Schema
-from pyiceberg.typedef import L, StructProtocol
+from pyiceberg.typedef import IcebergBaseModel, L, StructProtocol
 from pyiceberg.types import DoubleType, FloatType, NestedField
 from pyiceberg.utils.singleton import Singleton
 
@@ -329,21 +331,27 @@ def __getnewargs__(self) -> Tuple[BooleanExpression, BooleanExpression]:
         return (self.left, self.right)
 
 
-class Not(BooleanExpression):
+class Not(IcebergBaseModel, BooleanExpression):
     """NOT operation expression - logical negation."""
 
     child: BooleanExpression
 
-    def __new__(cls, child: BooleanExpression) -> BooleanExpression:  # type: ignore
+    @model_validator(mode="before")
+    def _before(cls, values: Any) -> Any:
+        if isinstance(values, BooleanExpression):
+            return {"child": values}
+        return values
+
+    @model_validator(mode="after")
+    def _normalize(cls, model: Any) -> Any:
+        child = model.child
         if child is AlwaysTrue():
             return AlwaysFalse()
         elif child is AlwaysFalse():
             return AlwaysTrue()
         elif isinstance(child, Not):
             return child.child
-        obj = super().__new__(cls)
-        obj.child = child
-        return obj
+        return model
 
     def __repr__(self) -> str:
         """Return the string representation of the Not class."""