Add multiple LangGraph examples including basic agents, chatbots, conditional edges, checkpointers, tool calls, and human-in-the-loop approval processes. Update .gitignore to include local environment files.

04_checkpointer.py

@@ -0,0 +1,64 @@
+from typing import Annotated, TypedDict
+
+from langchain_openai import ChatOpenAI
+from langgraph.checkpoint.memory import MemorySaver
+from langgraph.graph import StateGraph, START, END
+from langgraph.graph.message import add_messages
+
+
+class State(TypedDict):
+    messages: Annotated[list, add_messages]
+
+
+model = ChatOpenAI(
+    model="deepseek-v4-flash",
+    temperature=0,
+    base_url="https://api.deepseek.com/v1"
+)
+
+
+def chatbot(state: State):
+    return {
+        "messages": [model.invoke(state["messages"])]
+    }
+
+
+builder = StateGraph(State)
+builder.add_node("chatbot", chatbot)
+builder.add_edge(START, "chatbot")
+builder.add_edge("chatbot", END)
+
+checkpointer = MemorySaver()
+graph = builder.compile(checkpointer=checkpointer)
+
+config = {
+    "configurable": {
+        "thread_id": "user-001",
+    }
+}
+
+first = graph.invoke(
+    {
+        "messages": [
+            {
+                "role": "user",
+                "content": "我叫小明，请记住。",
+            }
+        ]
+    },
+    config=config,
+)
+
+second = graph.invoke(
+    {
+        "messages": [
+            {
+                "role": "user",
+                "content": "我叫什么名字？",
+            }
+        ]
+    },
+    config=config,
+)
+
+print(second["messages"][-1].content)