Docs: add save and load model docs. (#5397)

* docs: add save and load model docs.

* fix: update code style.

* fix: update code style.

* fix: fix typo and modify wording.

* docs: add save model example to notebook.

* fix: fix typo.

docs/readthedocs/source/doc/Orca/QuickStart/orca-tf2keras-quickstart.md

@@ -118,6 +118,34 @@ est.shutdown()
 print(stats)
 ```
 
+### **Step5: Save and Load the Model**
+
+Orca TF2 Estimator supports two formats to save and load the entire model (**TensorFlow SavedModel and Keras H5 Format**). The recommended format is SavedModel, which is the default format when you use `estimator.save()`.
+
+You could also save the model to Keras H5 format by passing `save_format='h5'` or a filename that ends in `.h5` or `.keras` to `estimator.save()`.
+
+**Note that if you run on Apache Hadoop/YARN cluster, you are recommended to save the model to HDFS and load from HDFS as well.**
+
+**1. SavedModel Format**
+
+```python
+# save model in SavedModel format
+estimator.save("/tmp/cifar10_model")
+
+# load model
+estimator.load("/tmp/cifar10_model")
+```
+
+**2. HDF5 format**
+
+```python
+# save model in H5 format
+estimator.save("/tmp/cifar10_model.h5", save_format='h5')
+
+# load model
+estimator.load("/tmp/cifar10_model.h5")
+```
+
 That's it, the same code can run seamlessly in your local laptop and to distribute K8s or Hadoop cluster.
 
 **Note:** You should call `stop_orca_context()` when your program finishes.