def check_duplicates(lines, previousSymbols):
    (ifndef_symbol, _) = get_ifndef_symbol(lines)
    if (ifndef_symbol in previousSymbols):
        return (False, ifndef_symbol)
    else:
        return (True, ifndef_symbol)
def check_duplicates(lines, previousSymbols):
    (ifndef_symbol, _) = get_ifndef_symbol(lines)
    if (ifndef_symbol in previousSymbols):
        return (False, ifndef_symbol)
    else:
        return (True, ifndef_symbol)