Update README

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

README.md

@@ -4,7 +4,7 @@
 
 <br />
 
-## Desription
+## Description
 
 An image embedding operator generates a vector given an image.
 This operator extracts features for image top ranked models from
@@ -18,22 +18,25 @@ The default pretrained model weights are from [The 1st Place Solution of ISC21 (
 Load an image from path './towhee.jpg'
 and use the pretrained ISC 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.jpg')
-          .image_decode()
-          .image_embedding.isc()
-          .show()
+p = (
+    pipe.input('path')
+        .map('path', 'img', ops.image_decode())
+        .map('img', 'vec', ops.image_embedding.isc())
+        .output('img', 'vec')
 )
-```
-<img src="./result1.png" height="50px"/>
 
-*Write a same pipeline with explicit inputs/outputs name specifications:*
+DataCollection(p('towhee.jpeg')).show()
+```
+<img src="./result.png" height="150px"/>
 
+- **option 2:**
 ```python
 import towhee
 
@@ -45,7 +48,6 @@ import towhee
           .show()
 )
 ```
-<img src="./result2.png" height="150px"/>
 
 <br />
 
@@ -83,10 +85,32 @@ It uses the pre-trained model specified by model name to generate an image embed
 The decoded image data in numpy.ndarray.
 
 
-
 **Returns:** *numpy.ndarray*
 
 The image embedding extracted by model.
 
+<br />
+
+***save_model(format='pytorch', path='default')***
+
+Save model to local with specified format.
+
+**Parameters:**
+
+***format***: *str*
+
+​	The format of saved model, defaults to 'pytorch'.
+
+***path***: *str*
+
+​	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.isc().get_op()
+op.save_model('onnx', 'test.onnx')
+```
+