Update gemma3_causal_lm_preprocessor.py (keras-team#2217)

* Update gemma3_causal_lm_preprocessor.py

Added checks for invalid inputs

* Update gemma3_causal_lm_preprocessor.py

* Update gemma3_causal_lm_preprocessor_test.py

Added tests to check invalid inputs

Author: pctablet505

keras_hub/src/models/gemma3/gemma3_causal_lm_preprocessor.py

@@ -512,6 +512,7 @@ def call(
 
         # Extract text part of the input.
         prompts, responses = x["prompts"], x["responses"]
+        tf.debugging.assert_shapes([(prompts, ("N",)), (responses, ("N",))])
 
         # Find out if the input is batched/not batched. Uprank if not batched.
         # In other preprocessors, we don't have to do this, but here, all

keras_hub/src/models/gemma3/gemma3_causal_lm_preprocessor_test.py

@@ -167,6 +167,20 @@ def test_generate_postprocess(self):
         x = preprocessor.generate_postprocess(input_data)
         self.assertAllEqual(x, "the quick brown fox \n\n <start_of_image>")
 
+    def test_invalid_shape(self):
+        with self.assertRaises(ValueError):
+            input_data = {
+                "prompts": ["hello world", "this is testing"],
+                "responses": [""],
+            }
+            self.text_preprocessor(input_data)
+        with self.assertRaises(ValueError):
+            input_data = {
+                "prompts": ["hello world", "this is testing"],
+                "responses": ["hello", "", ""],
+            }
+            self.text_preprocessor(input_data)
+
     @pytest.mark.kaggle_key_required
     @pytest.mark.extra_large
     def test_all_presets(self):