refactor: Update options for OpenAI in agent.rs file

examples/agent.rs

@@ -2,24 +2,22 @@ use std::sync::Arc;
 
 use langchain_rust::{
     agent::{AgentExecutor, ChatOutputParser, ConversationalAgentBuilder},
-    chain::Chain,
-    language_models::options::CallOptions,
-    llm::openai::{OpenAI, OpenAIModel},
+    chain::{options::ChainCallOptions, Chain},
+    llm::openai::OpenAI,
     memory::SimpleMemory,
     prompt_args,
     tools::Wolfram,
 };
 
 #[tokio::main]
 async fn main() {
-    let llm = OpenAI::default()
-        .with_model(OpenAIModel::Gpt4)
-        .with_options(CallOptions::default().with_max_tokens(1000));
+    let llm = OpenAI::default();
     let memory = SimpleMemory::new();
     let wolfram_tool = Wolfram::default();
     let agent = ConversationalAgentBuilder::new()
         .tools(vec![Arc::new(wolfram_tool)])
         .output_parser(ChatOutputParser::new().into())
+        .options(ChainCallOptions::new().with_max_tokens(1000))
         .build(llm)
         .unwrap();