Fix Keras import

keras_nlp/backend/__init__.py

@@ -27,6 +27,11 @@
 """
 
 from keras_nlp.backend import config
-from keras_nlp.backend import keras
-from keras_nlp.backend import ops
-from keras_nlp.backend import random
+
+if config.keras_3():
+    import keras  # noqa: E402
+else:
+    import keras_nlp.backend.keras2 as keras  # noqa: E402
+
+from keras_nlp.backend import ops  # noqa: E402
+from keras_nlp.backend import random  # noqa: E402

keras_nlp/backend/keras2.py

@@ -0,0 +1,42 @@
+# Copyright 2023 The KerasNLP Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import types
+
+try:
+    import tensorflow as tf
+except ImportError:
+    raise ImportError(
+        "To use `keras_nlp`, please install Tensorflow: "
+        "`pip install tensorflow`. The TensorFlow package is required for "
+        "data preprocessing with any backend."
+    )
+
+from tensorflow.keras import *  # noqa: F403, F401
+from tensorflow.keras import utils
+
+from keras_nlp.backend import config  # noqa: F401
+
+# Shims to handle symbol renames for older `tf.keras` versions.
+if not hasattr(tf.keras, "saving"):
+    saving = types.SimpleNamespace()
+else:
+    from tensorflow.keras import saving
+
+if not hasattr(saving, "deserialize_keras_object"):
+    saving.deserialize_keras_object = utils.deserialize_keras_object
+if not hasattr(saving, "serialize_keras_object"):
+    saving.serialize_keras_object = utils.serialize_keras_object
+if not hasattr(saving, "register_keras_serializable"):
+    saving.register_keras_serializable = utils.register_keras_serializable