roman to integer

print("Conversion from roman to arabic notation")
class Conversion:
    def convertionFunction(self, s:str) -> int:
        arabicConversion = {'M':1000, 'D':500, 'C':100, 'L':50, 'X':10, 'V':5, 'I':1}
        previousCharacter = 0
        currentCharacter = 0
        arabicNumber = 0
        for i in range(len(s)):
            currentCharacter = arabicConversion[s[i]]
            if currentCharacter > previousCharacter:
                arabicNumber = arabicNumber + currentCharacter - 2*previousCharacter
            else:
                arabicNumber += currentCharacter
            previousCharacter = currentCharacter
        return arabicNumber
print(Conversion().convertionFunction("MMMCCCXXXIII"))
print(Conversion().convertionFunction("MCXLIV"))
print(Conversion().convertionFunction("MCMXCIX"))
print(Conversion().convertionFunction("MCV"))
print(Conversion().convertionFunction("XCIX"))
print(Conversion().convertionFunction("MMMIX"))