Fix import of Keras (#2420)

* Fix import of Keras

* Fix import of Keras

* Fix import of Keras

* Fix Keras2 import

keras_cv/backend/__init__.py

@@ -26,7 +26,14 @@
 - `random`: `keras.random` for Keras 3 or `keras_core.ops` for Keras 2.
 """
 from keras_cv.backend import config  # noqa: E402
-from keras_cv.backend import keras  # noqa: E402
+
+if config.keras_3():
+    import keras  # noqa: E402
+
+    keras.backend.name_scope = keras.name_scope
+else:
+    import keras_cv.backend.keras2 as keras  # noqa: E402
+
 from keras_cv.backend import ops  # noqa: E402
 from keras_cv.backend import random  # noqa: E402
 from keras_cv.backend import tf_ops  # noqa: E402

keras_cv/backend/keras2.py

@@ -0,0 +1,59 @@
+# Copyright 2023 The KerasCV 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
+
+from tensorflow import keras  # noqa: F403, F401
+from tensorflow.keras import *  # noqa: F403, F401
+
+from keras_cv.backend import config  # noqa: F403, F401
+
+_KERAS_CORE_ALIASES = {
+    "utils->saving": [
+        "register_keras_serializable",
+        "deserialize_keras_object",
+        "serialize_keras_object",
+        "get_registered_object",
+    ],
+    "models->saving": ["load_model"],
+}
+
+if not hasattr(keras, "saving"):
+    keras.saving = types.SimpleNamespace()
+
+# add aliases
+for key, value in _KERAS_CORE_ALIASES.items():
+    src, _, dst = key.partition("->")
+    src = src.split(".")
+    dst = dst.split(".")
+
+    src_mod, dst_mod = keras, keras
+
+    # navigate to where we want to alias the attributes
+    for mod in src:
+        src_mod = getattr(src_mod, mod)
+    for mod in dst:
+        dst_mod = getattr(dst_mod, mod)
+
+    # add an alias for each attribute
+    for attr in value:
+        if isinstance(attr, tuple):
+            src_attr, dst_attr = attr
+        else:
+            src_attr, dst_attr = attr, attr
+        attr_val = getattr(src_mod, src_attr)
+        setattr(dst_mod, dst_attr, attr_val)
+
+# TF Keras doesn't have this rename.
+keras.activations.silu = keras.activations.swish