## Description
make DashScope models support Partial Mode for text continuation.
For text continuation in ChatTongYi, it supports text continuation with
a prefix by adding a "partial" argument in AIMessage. The document is
[Partial Mode
](https://help.aliyun.com/zh/model-studio/user-guide/partial-mode?spm=a2c4g.11186623.help-menu-2400256.d_1_0_0_8.211e5b77KMH5Pn&scm=20140722.H_2862210._.OR_help-T_cn~zh-V_1).
The API example is:
```py
import os
import dashscope
messages = [{
"role": "user",
"content": "请对“春天来了，大地”这句话进行续写，来表达春天的美好和作者的喜悦之情"
},
{
"role": "assistant",
"content": "春天来了，大地",
"partial": True
}]
response = dashscope.Generation.call(
api_key=os.getenv("DASHSCOPE_API_KEY"),
model='qwen-plus',
messages=messages,
result_format='message',
)
print(response.output.choices[0].message.content)
```
---------
Co-authored-by: Chester Curme <chester.curme@gmail.com>
