Fix typing.cast when subclassing (#20149)

keras/src/models/functional.py

@@ -96,7 +96,7 @@ class Functional(Function, Model):
     """
 
     def __new__(cls, *args, **kwargs):
-        return typing.cast(Functional, super().__new__(cls))
+        return typing.cast(cls, super().__new__(cls))
 
     @tracking.no_automatic_dependency_tracking
     def __init__(self, inputs, outputs, name=None, **kwargs):

keras/src/models/model.py

@@ -141,7 +141,7 @@ def __new__(cls, *args, **kwargs):
             from keras.src.models.functional import Functional
 
             return Functional.__new__(Functional, *args, **kwargs)
-        return typing.cast(Model, super().__new__(cls))
+        return typing.cast(cls, super().__new__(cls))
 
     def __init__(self, *args, **kwargs):
         Trainer.__init__(self)

keras/src/models/sequential.py

@@ -63,7 +63,7 @@ class Sequential(Model):
     """
 
     def __new__(cls, *args, **kwargs):
-        return typing.cast(Sequential, super().__new__(cls))
+        return typing.cast(cls, super().__new__(cls))
 
     def __init__(self, layers=None, trainable=True, name=None):
         super().__init__(trainable=trainable, name=name)