[Python] Python UnboundLocalError even though the variable is in the same function and defined...

I have this code on my Flask app, few of them are these lines.

@app.post("/dashboard/model/train/process")
@login_required
def model_train_process():
#Really a lot of code...
possible_parameter : ["categorical", "int", "float", "boolean"] # type: ignore
for param in possible_parameter:
#I'm doing something inside here...


Just to be clear, I'm using # type: ignore because Pylance throw a warning because I'm using data type as a string value.

Back to the main topic, I don't know why but Python throw this error

UnboundLocalError: cannot access local variable 'possible_parameter' where it is not associated with a value
​

That variable already defined before the loop, they are both in the same function, so why this error happened?

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