feat: add lifecycle hooks to agent

Author: uzair330

src/agents/lifecycle.py

@@ -10,6 +10,29 @@ class RunHooks(Generic[TContext]):
     override the methods you need.
     """
 
+    #Two new hook methods added to the RunHooks class to handle LLM start and end events.
+    #These methods allow you to perform actions just before and after the LLM call for an agent.
+    #This is useful for logging, monitoring, or modifying the context before and after the LLM call.
+    async def on_llm_start(
+        self,
+        context: RunContextWrapper[TContext],
+        agent: Agent[TContext],
+        system_prompt: str | None,
+        input_items: List[TResponseInputItem]
+    ) -> None:
+        """Called just before invoking the LLM for this agent."""
+        pass
+
+    async def on_llm_end(
+        self,
+        context: RunContextWrapper[TContext],
+        agent: Agent[TContext],
+        response: ModelResponse
+    ) -> None:
+        """Called immediately after the LLM call returns for this agent."""
+        pass
+    
+
     async def on_agent_start(
         self, context: RunContextWrapper[TContext], agent: Agent[TContext]
     ) -> None: