[translation] Fix export by fixing export utils so that by default is used...

[translation] Fix export by fixing export utils so that by default is used model.call and not model.__call__ which contains keras extra tracing logic.

PiperOrigin-RevId: 430546354

official/core/export_base.py

@@ -67,6 +67,15 @@ class ExportModule(tf.Module, metaclass=abc.ABCMeta):
 
     if inference_step is not None:
       self.inference_step = functools.partial(inference_step, model=self.model)
+    else:
+      if issubclass(type(model), tf.keras.Model):
+        # Default to self.model.call instead of self.model.__call__ to avoid
+        # keras tracing logic designed for training.
+        # Since most of Model Garden's call doesn't not have training kwargs
+        # or the default is False, we don't pass anything here.
+        # Please pass custom inference step if your model has training=True as
+        # default.
+        self.inference_step = self.model.call
       else:
         self.inference_step = functools.partial(
             self.model.__call__, training=False)

official/nlp/serving/serving_modules_test.py

@@ -20,6 +20,7 @@ from absl.testing import parameterized
 import tensorflow as tf
 
 from sentencepiece import SentencePieceTrainer
+from official.core import export_base
 from official.nlp.configs import bert
 from official.nlp.configs import encoders
 from official.nlp.serving import serving_modules
@@ -369,5 +370,18 @@ class ServingModulesTest(tf.test.TestCase, parameterized.TestCase):
     self.assertEqual(outputs.shape, (2,))
     self.assertEqual(outputs.dtype, tf.string)
 
+    tmp_dir = self.get_temp_dir()
+    export_base_dir = os.path.join(tmp_dir, "export")
+    ckpt_dir = os.path.join(tmp_dir, "ckpt")
+    ckpt_path = tf.train.Checkpoint(model=model).save(ckpt_dir)
+    export_dir = export_base.export(export_module,
+                                    {"serve_text": "serving_default"},
+                                    export_base_dir, ckpt_path)
+    loaded = tf.saved_model.load(export_dir)
+    infer = loaded.signatures["serving_default"]
+    out = infer(text=tf.constant(["abcd", "ef gh"]))
+    self.assertLen(out["output_0"], 2)
+
+
 if __name__ == "__main__":
   tf.test.main()