community: make DashScope models support Partial Mode for text continuation. (#30108)

## 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>

docs/docs/integrations/chat/tongyi.ipynb

@@ -26,22 +26,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
-   "metadata": {
-    "collapsed": false,
-    "jupyter": {
-     "outputs_hidden": false
-    }
-   },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "Note: you may need to restart the kernel to use updated packages.\n"
-     ]
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "# Install the package\n",
     "%pip install --upgrade --quiet  dashscope"
@@ -49,8 +36,12 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 1,
    "metadata": {
+    "ExecuteTime": {
+     "end_time": "2025-03-05T01:11:20.457141Z",
+     "start_time": "2025-03-05T01:11:18.810160Z"
+    },
     "collapsed": false,
     "jupyter": {
      "outputs_hidden": false
@@ -66,8 +57,12 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": 2,
    "metadata": {
+    "ExecuteTime": {
+     "end_time": "2025-03-05T01:11:24.270318Z",
+     "start_time": "2025-03-05T01:11:24.268064Z"
+    },
     "collapsed": false,
     "jupyter": {
      "outputs_hidden": false
@@ -266,6 +261,52 @@
     "ai_message"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Partial Mode\n",
+    "Enable the large model to continue generating content from the initial text you provide."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {
+    "ExecuteTime": {
+     "end_time": "2025-03-05T01:31:29.155824Z",
+     "start_time": "2025-03-05T01:31:27.239667Z"
+    }
+   },
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "AIMessage(content=' has cast off its heavy cloak of snow, donning instead a vibrant garment of fresh greens and floral hues; it is as if the world has woken from a long slumber, stretching and reveling in the warm caress of the sun. Everywhere I look, there is a symphony of life: birdsong fills the air, bees dance from flower to flower, and a gentle breeze carries the sweet fragrance of blossoms. It is in this season that my heart finds particular joy, for it whispers promises of renewal and growth, reminding me that even after the coldest winters, there will always be a spring to follow.', additional_kwargs={}, response_metadata={'model_name': 'qwen-turbo', 'finish_reason': 'stop', 'request_id': '447283e9-ee31-9d82-8734-af572921cb05', 'token_usage': {'input_tokens': 40, 'output_tokens': 127, 'prompt_tokens_details': {'cached_tokens': 0}, 'total_tokens': 167}}, id='run-6a35a91c-cc12-4afe-b56f-fd26d9035357-0')"
+      ]
+     },
+     "execution_count": 4,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "from langchain_community.chat_models.tongyi import ChatTongyi\n",
+    "from langchain_core.messages import AIMessage, HumanMessage\n",
+    "\n",
+    "messages = [\n",
+    "    HumanMessage(\n",
+    "        content=\"\"\"Please continue the sentence \"Spring has arrived, and the earth\" to express the beauty of spring and the author's joy.\"\"\"\n",
+    "    ),\n",
+    "    AIMessage(\n",
+    "        content=\"Spring has arrived, and the earth\", additional_kwargs={\"partial\": True}\n",
+    "    ),\n",
+    "]\n",
+    "chatLLM = ChatTongyi()\n",
+    "ai_message = chatLLM.invoke(messages)\n",
+    "ai_message"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},

libs/community/langchain_community/chat_models/tongyi.py

@@ -123,6 +123,8 @@ def convert_dict_to_message(
                             tool_calls.append(parsed_tool)
                     except Exception as e:
                         invalid_tool_calls.append(make_invalid_tool_call(value, str(e)))
+        elif "partial" in _dict and isinstance(_dict["partial"], bool):
+            additional_kwargs = {"partial": _dict["partial"]}
         else:
             additional_kwargs = {}
 
@@ -204,6 +206,9 @@ def convert_message_to_dict(message: BaseMessage) -> dict:
         message_dict = {"role": "assistant", "content": message.content}
         if "tool_calls" in message.additional_kwargs:
             message_dict["tool_calls"] = message.additional_kwargs["tool_calls"]
+        # support Partial Mode for text continuation
+        if "partial" in message.additional_kwargs:
+            message_dict["partial"] = message.additional_kwargs["partial"]
     elif isinstance(message, SystemMessage):
         message_dict = {"role": "system", "content": message.content}
     elif isinstance(message, ToolMessage):

libs/community/tests/unit_tests/chat_models/test_tongyi.py

@@ -65,6 +65,13 @@ def test__convert_dict_to_message_function_call() -> None:
     assert result == expected_output
 
 
+def test__convert_dict_to_message_partial_mode() -> None:
+    message_dict = {"role": "assistant", "content": "foo", "partial": True}
+    result = convert_dict_to_message(message_dict)
+    expected_output = AIMessage(content="foo", additional_kwargs={"partial": True})
+    assert result == expected_output
+
+
 def test__convert_message_to_dict_human() -> None:
     message = HumanMessage(content="foo")
     result = convert_message_to_dict(message)
@@ -79,6 +86,13 @@ def test__convert_message_to_dict_ai() -> None:
     assert result == expected_output
 
 
+def test__convert_message_to_dict_ai_partial_mode() -> None:
+    message = AIMessage(content="foo", additional_kwargs={"partial": True})
+    result = convert_message_to_dict(message)
+    expected_output = {"role": "assistant", "content": "foo", "partial": True}
+    assert result == expected_output
+
+
 def test__convert_message_to_dict_system() -> None:
     message = SystemMessage(content="foo")
     result = convert_message_to_dict(message)