def exclude_options(string, list_to_exclude):
    """Confirm input is not in a given list.

    Return the input if yes; raise an error if not. 
    Case sensitive.
    """
    try:
        assert string not in list_to_exclude
    except AssertionError:
        raise RuntimeError(f"Input may not be one of {list_to_exclude}.")
    
    return string