Adds error for serializing metric using layer serialization.

PiperOrigin-RevId: 527991285

Author: nkovela1

keras/layers/serialization.py

@@ -50,6 +50,7 @@
 from keras.layers.rnn import cell_wrappers
 from keras.layers.rnn import gru
 from keras.layers.rnn import lstm
+from keras.metrics import base_metric
 from keras.saving import serialization_lib
 from keras.saving.legacy import serialization as legacy_serialization
 from keras.saving.legacy.saved_model import json_utils
@@ -208,6 +209,13 @@ def serialize(layer, use_legacy_format=False):
     pprint(tf.keras.layers.serialize(model))
     # prints the configuration of the model, as a dict.
     """
+    if isinstance(layer, base_metric.Metric):
+        raise ValueError(
+            f"Cannot serialize {layer} since it is a metric. "
+            "Please use the `keras.metrics.serialize()` and "
+            "`keras.metrics.deserialize()` APIs to serialize "
+            "and deserialize metrics."
+        )
     if use_legacy_format:
         return legacy_serialization.serialize_keras_object(layer)
 

keras/layers/serialization_test.py

@@ -24,6 +24,7 @@
 from keras.layers.rnn import gru_v1
 from keras.layers.rnn import lstm
 from keras.layers.rnn import lstm_v1
+from keras.metrics import Mean
 from keras.testing_infra import test_combinations
 
 
@@ -191,6 +192,11 @@ def test_serialize_deserialize_gru(self, layer):
             self.assertIsInstance(new_layer, gru_v1.GRU)
             self.assertNotIsInstance(new_layer, gru.GRU)
 
+    def test_serialize_metric_throws_error(self):
+        metric = Mean()
+        with self.assertRaisesRegex(ValueError, "since it is a metric."):
+            _ = keras.layers.serialize(metric)
+
 
 if __name__ == "__main__":
     tf.test.main()