feat: Implement stream interface (#15875)

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Major changes:

- Rename `wasm_chat.py` to `llama_edge.py`
- Rename the `WasmChatService` class to `ChatService`
- Implement the `stream` interface for `ChatService`
- Add `test_chat_wasm_service_streaming` in the integration test
- Update `llama_edge.ipynb`

---------

Signed-off-by: Xin Liu <sam@secondstate.io>

libs/community/tests/integration_tests/chat_models/test_llama_edge.py

@@ -0,0 +1,52 @@
+import pytest
+from langchain_core.messages import AIMessage, HumanMessage, SystemMessage
+
+from langchain_community.chat_models.llama_edge import LlamaEdgeChatService
+
+
+@pytest.mark.enable_socket
+def test_chat_wasm_service() -> None:
+    """This test requires the port 8080 is not occupied."""
+
+    # service url
+    service_url = "https://b008-54-186-154-209.ngrok-free.app"
+
+    # create wasm-chat service instance
+    chat = LlamaEdgeChatService(service_url=service_url)
+
+    # create message sequence
+    system_message = SystemMessage(content="You are an AI assistant")
+    user_message = HumanMessage(content="What is the capital of France?")
+    messages = [system_message, user_message]
+
+    # chat with wasm-chat service
+    response = chat(messages)
+
+    # check response
+    assert isinstance(response, AIMessage)
+    assert isinstance(response.content, str)
+    assert "Paris" in response.content
+
+
+@pytest.mark.enable_socket
+def test_chat_wasm_service_streaming() -> None:
+    """This test requires the port 8080 is not occupied."""
+
+    # service url
+    service_url = "https://b008-54-186-154-209.ngrok-free.app"
+
+    # create wasm-chat service instance
+    chat = LlamaEdgeChatService(service_url=service_url, streaming=True)
+
+    # create message sequence
+    user_message = HumanMessage(content="What is the capital of France?")
+    messages = [
+        user_message,
+    ]
+
+    output = ""
+    for chunk in chat.stream(messages):
+        print(chunk.content, end="", flush=True)
+        output += chunk.content
+
+    assert "Paris" in output

libs/community/tests/integration_tests/chat_models/test_wasm_chat.py

@@ -1,28 +0,0 @@
-import pytest
-from langchain_core.messages import AIMessage, HumanMessage, SystemMessage
-
-from langchain_community.chat_models.wasm_chat import WasmChatService
-
-
-@pytest.mark.enable_socket
-def test_chat_wasm_service() -> None:
-    """This test requires the port 8080 is not occupied."""
-
-    # service url
-    service_url = "https://b008-54-186-154-209.ngrok-free.app"
-
-    # create wasm-chat service instance
-    chat = WasmChatService(service_url=service_url)
-
-    # create message sequence
-    system_message = SystemMessage(content="You are an AI assistant")
-    user_message = HumanMessage(content="What is the capital of France?")
-    messages = [system_message, user_message]
-
-    # chat with wasm-chat service
-    response = chat(messages)
-
-    # check response
-    assert isinstance(response, AIMessage)
-    assert isinstance(response.content, str)
-    assert "Paris" in response.content