add warning if duplicate function is registered

autogen/agentchat/conversable_agent.py

@@ -2579,6 +2579,9 @@ def _decorator(func: F) -> F:
             elif not hasattr(func, "_name"):
                 func._name = func.__name__
 
+            if (func._name in self._function_map) or (self.llm_config and "tools" in self.llm_config.keys() and func._name in [tool["function"]["name"] for tool in self.llm_config["tools"]]):
+                warnings.warn(f"Function '{func._name}' is being overridden.", UserWarning)
+
             self.register_function({func._name: self._wrap_function(func)})
 
             return func