def check_invalid(string,*invalids,defaults=True):
    """Checks if input string matches an invalid value"""

    # Checks string against inputted invalid values
    for v in invalids:
        if string == v:
            return True

    # Checks string against default invalid values, if defaults=True
    if  defaults == True:
        default_invalids = ['INC','inc','incomplete','NaN','nan','N/A','n/a','missing']
        for v in default_invalids:
            if string == v:
                return True

    # For valid strings 
    return False