Add pipeline example

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

README.md

@@ -23,7 +23,7 @@ from towhee import pipe, ops
 
 p = (
     pipe.input('messages')
-        .map('messages', 'answer', ops.LLM.Ernie(api_key=ERNIE_API_KEY, secret_key=ERNIE_SECRET_KEY))
+        .map('messages', 'answer', ops.LLM.Ernie(api_key=ERNIE_API_KEY, secret_key=ERNIE_SECRET_KEY, temperature=0.5))
         .output('answer')
 )
 
@@ -34,6 +34,38 @@ messages=[
 answer = p(messages).get()[0]
 ```
 
+*Write a [retrieval-augmented generation pipeline](https://towhee.io/tasks/detail/pipeline/retrieval-augmented-generation) with explicit inputs/outputs name specifications:*
+
+```python
+from towhee import pipe, ops
+
+
+temp = '''根据以下材料回答最末尾的问题：
+
+{context}
+
+问题：{question}
+'''
+
+
+docs = ['你可以通过`pip install towhee` 安装 Towhee。']
+history = [
+    ('什么是 Towhee？', 'Towhee 是一个开源项目，可以将非结构化数据转换为向量。')
+]
+question = '怎么安装它？'
+
+p = (
+    pipe.input('question', 'docs', 'history')
+        .map(('question', 'docs', 'history'), 'prompt', ops.prompt.template(temp, ['question', 'context']))
+        .map('prompt', 'answer',
+             ops.LLM.Ernie(api_key=ERNIE_API_KEY, secret_key=ERNIE_SECRET_KEY)
+             )
+        .output('answer')
+)
+
+answer = p(question, docs, history).get()[0]
+```
+
 <br />
 
 ## Factory Constructor 接口说明
@@ -55,7 +87,7 @@ The Ernie Secret key in string, defaults to None. If None, it will use the envir
 
 ***\*\*kwargs***
 
-Other OpenAI parameters such as temperature, etc.
+Other Ernie parameters such as temperature, etc.
 
 <br />