docs: fix delete_old_messages example to properly demonstrate deletion effect (#4009)

Author: uditstocks

src/oss/langchain/short-term-memory.mdx

@@ -392,6 +392,13 @@ for event in agent.stream(
 ):
     print([(message.type, message.content) for message in event["messages"]])
 
+for event in agent.stream(
+    {"messages": [{"role": "user", "content": "write a short poem about cats"}]},
+    config,
+    stream_mode="values",
+):
+    print([(message.type, message.content) for message in event["messages"]])
+
 for event in agent.stream(
     {"messages": [{"role": "user", "content": "what's my name?"}]},
     config,
@@ -403,9 +410,12 @@ for event in agent.stream(
 ```
 [('human', "hi! I'm bob")]
 [('human', "hi! I'm bob"), ('ai', 'Hi Bob! Nice to meet you. How can I help you today? I can answer questions, brainstorm ideas, draft text, explain things, or help with code.')]
-[('human', "hi! I'm bob"), ('ai', 'Hi Bob! Nice to meet you. How can I help you today? I can answer questions, brainstorm ideas, draft text, explain things, or help with code.'), ('human', "what's my name?")]
-[('human', "hi! I'm bob"), ('ai', 'Hi Bob! Nice to meet you. How can I help you today? I can answer questions, brainstorm ideas, draft text, explain things, or help with code.'), ('human', "what's my name?"), ('ai', 'Your name is Bob. How can I help you today, Bob?')]
-[('human', "what's my name?"), ('ai', 'Your name is Bob. How can I help you today, Bob?')]
+[('human', "hi! I'm bob"), ('ai', 'Hi Bob! Nice to meet you. How can I help you today? I can answer questions, brainstorm ideas, draft text, explain things, or help with code.'), ('human', "write a short poem about cats")]
+[('human', "hi! I'm bob"), ('ai', 'Hi Bob! Nice to meet you. How can I help you today? I can answer questions, brainstorm ideas, draft text, explain things, or help with code.'), ('human', "write a short poem about cats"), ('ai', 'There once was a cat on a wall, Who barely moved at all...')]
+[('human', 'write a short poem about cats'), ('ai', 'There once was a cat on a wall, Who barely moved at all...')]
+[('human', 'write a short poem about cats'), ('ai', 'There once was a cat on a wall, Who barely moved at all...'), ('human', "what's my name?")]
+[('human', 'write a short poem about cats'), ('ai', 'There once was a cat on a wall, Who barely moved at all...'), ('human', "what's my name?"), ('ai', "I don't know your name - you haven't told me!")]
+[('human', "what's my name?"), ('ai', "I don't know your name - you haven't told me!")]
 ```
 :::
 
@@ -454,9 +464,7 @@ for await (const event of streamA) {
 }
 
 const streamB = await agent.stream(
-  {
-    messages: [{ role: "user", content: "what's my name?" }],
-  },
+  { messages: [{ role: "user", content: "write a short poem about cats" }] },
   { ...config, streamMode: "values" }
 );
 for await (const event of streamB) {
@@ -466,15 +474,29 @@ for await (const event of streamB) {
   ]);
   console.log(messageDetails);
 }
+
+const streamC = await agent.stream(
+  { messages: [{ role: "user", content: "what's my name?" }] },
+  { ...config, streamMode: "values" }
+);
+for await (const event of streamC) {
+  const messageDetails = event.messages.map((message) => [
+    message.getType(),
+    message.content,
+  ]);
+  console.log(messageDetails);
+}
 ```
 
 ```
-[[ "human", "hi! I'm bob" ]]
-[[ "human", "hi! I'm bob" ], [ "ai", "Hello, Bob! How can I assist you today?" ]]
-[[ "human", "hi! I'm bob" ], [ "ai", "Hello, Bob! How can I assist you today?" ]]
-[[ "human", "hi! I'm bob" ], [ "ai", "Hello, Bob! How can I assist you today" ], ["human", "what's my name?" ]]
-[[ "human", "hi! I'm bob" ], [ "ai", "Hello, Bob! How can I assist you today?" ], ["human", "what's my name?"], [ "ai", "Your name is Bob, as you mentioned. How can I help you further?" ]]
-[[ "human", "what's my name?" ], [ "ai", "Your name is Bob, as you mentioned. How can I help you further?" ]]
+[["human", "hi! I'm bob"]]
+[["human", "hi! I'm bob"], ["ai", "Hi Bob! Nice to meet you. How can I help you today? I can answer questions, brainstorm ideas, draft text, explain things, or help with code."]]
+[["human", "hi! I'm bob"], ["ai", "Hi Bob! Nice to meet you. How can I help you today? I can answer questions, brainstorm ideas, draft text, explain things, or help with code."], ["human", "write a short poem about cats"]]
+[["human", "hi! I'm bob"], ["ai", "Hi Bob! Nice to meet you. How can I help you today? I can answer questions, brainstorm ideas, draft text, explain things, or help with code."], ["human", "write a short poem about cats"], ["ai", "There once was a cat on a wall, Who barely moved at all..."]]
+[["human", "write a short poem about cats"], ["ai", "There once was a cat on a wall, Who barely moved at all..."]]
+[["human", "write a short poem about cats"], ["ai", "There once was a cat on a wall, Who barely moved at all..."], ["human", "what's my name?"]]
+[["human", "write a short poem about cats"], ["ai", "There once was a cat on a wall, Who barely moved at all..."], ["human", "what's my name?"], ["ai", "I don't know your name - you haven't told me!"]]
+[["human", "what's my name?"], ["ai", "I don't know your name - you haven't told me!"]]
 ```
 :::