Ellipsis Serialization and tests (#19564)

* Serialization and tests

* Serialization and tests

* Serialization and tests

keras/src/saving/serialization_lib.py

@@ -162,6 +162,11 @@ def serialize_keras_object(obj):
                 "step": serialize_keras_object(obj.step),
             },
         }
+    # Ellipsis is an instance, and ellipsis class is not in global scope.
+    # checking equality also fails elsewhere in the library, so we have
+    # to dynamically get the type.
+    if isinstance(obj, type(Ellipsis)):
+        return {"class_name": "__ellipsis__", "config": {}}
     if isinstance(obj, backend.KerasTensor):
         history = getattr(obj, "_keras_history", None)
         if history:
@@ -613,6 +618,8 @@ class ModifiedMeanSquaredError(keras.losses.MeanSquaredError):
         return np.array(inner_config["value"], dtype=inner_config["dtype"])
     if config["class_name"] == "__bytes__":
         return inner_config["value"].encode("utf-8")
+    if config["class_name"] == "__ellipsis__":
+        return Ellipsis
     if config["class_name"] == "__slice__":
         return slice(
             deserialize_keras_object(

keras/src/saving/serialization_lib_test.py

@@ -107,6 +107,10 @@ def tuples_to_lists_str(x):
         reserialized_str = tuples_to_lists_str(reserialized)
         self.assertEqual(serialized_str, reserialized_str)
 
+    def test_serialize_ellipsis(self):
+        _, deserialized, _ = self.roundtrip(Ellipsis)
+        self.assertEqual(..., deserialized)
+
     def test_tensors_and_shapes(self):
         x = ops.random.normal((2, 2), dtype="float64")
         obj = {"x": x}