Update README

Signed-off-by: Jael Gu <mengjia.gu@zilliz.com>

README.md

@@ -18,20 +18,26 @@ who maintains SOTA deep-learning models and tools in computer vision.
 Load an image from path './towhee.jpeg'
 and use the pre-trained ResNet50 model ('resnet50') to generate an image embedding.
 
- *Write the pipeline in simplified style:*
+*Write a same pipeline with explicit inputs/outputs name specifications:*
+
+- **option 1:**
 
 ```python
-import towhee
+from towhee.dc2 import pipe, ops, DataCollection
 
-towhee.glob('./towhee.jpeg') \
-      .image_decode() \
-      .image_embedding.timm(model_name='resnet50') \
-      .show()
+p = (
+    pipe.input('path')
+        .map('path', 'img', ops.image_decode())
+        .map('img', 'vec', ops.image_embedding.timm(model_name='resnet50'))
+        .output('img', 'vec')
+)
+
+DataCollection(p('towhee.jpeg')).show()
 ```
-<img src="./result1.png" height="50px"/>
 
-*Write a same pipeline with explicit inputs/outputs name specifications:*
+<img src="./result.png" height="150px"/>
 
+- **option 2:**
 ```python
 import towhee
 
@@ -41,7 +47,6 @@ towhee.glob['path']('./towhee.jpeg') \
       .select['img', 'vec']() \
       .show()
 ```
-<img src="./result2.png" height="150px"/>
 
 <br />
 
@@ -104,6 +109,13 @@ Save model to local with specified format.
 
 ​	The path where model is saved to. By default, it will save model to the operator directory.
 
+```python
+from towhee import ops
+
+op = ops.image_embedding.timm(model_name='resnet50').get_op()
+op.save_model('onnx', 'test.onnx')
+```
+
 <br />
 
 ***supported_model_names(format=None)***