code: def test_update_tool():
      config_list_gpt4 = autogen.config_list_from_json(
          OAI_CONFIG_LIST,
          filter_dict={
              "model": [
                  "gpt-4",
                  "gpt-4-0314",
                  "gpt4",
                  "gpt-4-32k",
                  "gpt-4-32k-0314",
                  "gpt-4-32k-v0314",
              ],
          },
          file_location=KEY_LOC,
      )
      llm_config = {
          "config_list": config_list_gpt4,
          "seed": 42,
          "tools": [],
      }
  
      user_proxy = autogen.UserProxyAgent(
          name="user_proxy",
          human_input_mode="NEVER",
          is_termination_msg=lambda x: True
          if "TERMINATE" in x.get("content")
          else False,
      )
      assistant = autogen.AssistantAgent(
          name="test", llm_config=llm_config
      )
  
      # Define a new function *after* the assistant has been created
      assistant.update_tool_signature(
          {
              "type": "function",
              "function": {
                  "name": "greet_user",
                  "description": "Greets the user.",
                  "parameters": {
                      "type": "object",
                      "properties": {},
                      "required": [],
                  },
              },
          },
          is_remove=False,
      )
      user_proxy.initiate_chat(
          assistant,
          message="What functions do you know about in the context of this conversation? End your response with 'TERMINATE'.",
      )
      messages1 = assistant.chat_messages[user_proxy][-1]["content"]
      print(messages1)
  
      assistant.update_tool_signature("greet_user", is_remove=True)
      user_proxy.initiate_chat(
          assistant,
          message="What functions do you know about in the context of this conversation? End your response with 'TERMINATE'.",
      )
      messages2 = assistant.chat_messages[user_proxy][-1]["content"]
      print(messages2)
      # The model should know about the function in the context of the conversation
      assert "greet_user" in messages1
      assert "greet_user" not in messages2
  
file_path: autogen/test/agentchat/test_tool_calls.py
imports: import inspect
  import pytest
  import json
  import sys
  import os
  import autogen
  from autogen.math_utils import eval_math_responses
  from test_assistant_agent import KEY_LOC, OAI_CONFIG_LIST
  from autogen.oai.client import TOOL_ENABLED
label_desc: Use image node_id 3 for calling a global function with example usage: test_update_tool() without return types