Check if an input is a valid roman numeral

Question

I got a program that converts Roman numerals to integers and vice versa. My problem is that I don´t really know how to create a function that checks if the user input is a v

Answer 1

def checkIfRomanNumeral(numeral):
"""Controls that the userinput only contains valid roman numerals"""
    numeral = numeral.upper()
    validRomanNumerals = ["M", "D", "C", "L", "X", "V", "I", "(", ")"]
    valid = True
    for letters in numeral:
        if letters not in validRomanNumerals:
            print("Sorry that is not a valid roman numeral")
            valid = False
            break
    return valid

Returns a boolean whether the given 'numeral' is roman numeral or not.