Add tf_keras imports to prepare for Keras 3 (#28588)

* Port core files + ESM (because ESM code is odd)

* Search-replace in modelling code

* Fix up transfo_xl as well

* Fix other core files + tests (still need to add correct import to tests)

* Fix cookiecutter

* make fixup, fix imports in some more core files

* Auto-add imports to tests

* Cleanup, add imports to sagemaker tests

* Use correct exception for importing tf_keras

* Fixes in modeling_tf_utils

* make fixup

* Correct version parsing code

* Ensure the pipeline tests correctly revert to float32 after each test

* Ensure the pipeline tests correctly revert to float32 after each test

* More tf.keras -> keras

* Add dtype cast

* Better imports of tf_keras

* Add a cast for tf.assign, just in case

* Fix callback imports

examples/tensorflow/text-classification/run_text_classification.py

@@ -27,6 +27,7 @@ from typing import Optional
 
 import numpy as np
 from datasets import load_dataset
+from packaging.version import parse
 
 from transformers import (
     AutoConfig,
@@ -46,11 +47,24 @@ os.environ["TF_CPP_MIN_LOG_LEVEL"] = "1"  # Reduce the amount of console output
 import tensorflow as tf  # noqa: E402
 
 
+try:
+    import tf_keras as keras
+except (ModuleNotFoundError, ImportError):
+    import keras
+
+    if parse(keras.__version__).major > 2:
+        raise ValueError(
+            "Your currently installed version of Keras is Keras 3, but this is not yet supported in "
+            "Transformers. Please install the backwards-compatible tf-keras package with "
+            "`pip install tf-keras`."
+        )
+
+
 logger = logging.getLogger(__name__)
 
 
 # region Helper classes
-class SavePretrainedCallback(tf.keras.callbacks.Callback):
+class SavePretrainedCallback(keras.callbacks.Callback):
     # Hugging Face models have a save_pretrained() method that saves both the weights and the necessary
     # metadata to allow them to be loaded as a pretrained model in future. This is a simple Keras callback
     # that saves the model with this method after each epoch.