def get_fn_signature(fn: Callable) -> inspect.Signature:
    """Get the signature of a function.

    Args:
        fn: The function.

    Returns:
        The signature of the function.
    """
    signature = inspect.signature(fn)
    new_param = inspect.Parameter(
        FRONTEND_EVENT_STATE, inspect.Parameter.POSITIONAL_OR_KEYWORD, annotation=Any
    )
    return signature.replace(parameters=(new_param, *signature.parameters.values()))
Get the signature of a function.

    Args:
        fn: The function.

    Returns:
        The signature of the function.
    
reflex/event.py