Unable to pass self.instance_variable as default into a class method

I have a class and method that I am trying to pass a self.instance_variable as default but am unable to. Let me illustrate:

from openai import OpenAI

class Example_class:
    def __init__(self) -> None:
        self.client = OpenAI(api_key='xyz')
        self.client2 = OpenAI(api_key='abc')
    
    def chat_completion(self, prompt, context, client=self.client, model='gpt-4o'):
        # Process the prompt
        messages = [{"role": "system", "content": context}, {"role": "user", "content": prompt}]
        response = client.chat.completions.create(
            model=model,
            messages=messages,
            temperature=0.35, # this is the degree of randomness of the model's output
        )
        return response.choices[0].message.content
    
    def do_something(self):
        self.chat_completion(prompt="blah blah blah", context="fgasa")

You see, there is an error when trying to pass self.client into the chat_completion method. Where am I going wrong?

You simply cannot do it like this. Understand the "self" as an argument just like the others (it really is). You cannot access it directly from the function header

One "correct" way to do this is to define a default Value as None and check for it's content :

Class Example_class:
    def chat_completion(self, prompt, context, client=None, model='gpt-4o'):
        client = client or self.client # this will ensure client is never None.
        # Process the prompt