If GPT thinks a function call is warranted based on the input, then it fills in a "function_call" parameter in its response and provides the arguments. You then call the function using those arguments and in your next call to ChatCompletion, you pass in the response from your function.

  message = response["choices"][0]["message"]

    # Step 2, check if the model wants to call a function
    if message.get("function_call"):
        function_name = message["function_call"]["name"]

  ...

  second_response = openai.ChatCompletion.create(
            model="gpt-3.5-turbo-0613",
            messages=[
                {"role": "user", "content": "What is the weather like in boston?"},
                message,
                {
                    "role": "function",
                    "name": function_name,
                    "content": function_response,
                },
            ],
        )