title: Check if an input is a valid roman numeral
body: <p>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 valid roman numeral. My code right now:</p>
  
  <pre><code>def checkIfRomanNumeral(numeral):
  """Controls that the userinput only contains valid roman numerals"""
      numeral = numeral.upper()
      validRomanNumerals = ["M", "D", "C", "L", "X", "V", "I", "(", ")"]
      for letters in numeral:
          if letters not in validRomanNumerals:
              print("Sorry that is not a valid roman numeral")
              return True
          elif letters in validRomanNumerals:
              romanToInt(numeral)
              break
  </code></pre>
  
  <p>I think the problem right now is that the function only checks the first letter in the input(numeral) because of the for loop. Could someone help me to make the function check the whole input and print("Sorry that is not a valid Roman numeral") if any letter of the input is not a Roman numeral. The parenthesis in the list validRomanNumerals are used to convert numbers bigger than 4000 so they must be there.</p>