input: Write a python function to convert a Roman numeral string to an integer.
  assert convert_roman_to_int("III") == 3
  assert convert_roman_to_int("IV") == 4
  assert convert_roman_to_int("IX") == 9
  assert convert_roman_to_int("LVIII") == 58
  assert convert_roman_to_int("MCMXCIV") == 1994
output: def convert_roman_to_int(s):
      roman_to_int = {
          'I': 1,
          'V': 5,
          'X': 10,
          'L': 50,
          'C': 100,
          'D': 500,
          'M': 1000
      }
      
      total = 0
      prev_value = 0
      
      for char in reversed(s):
          current_value = roman_to_int[char]
          if current_value >= prev_value:
              total += current_value
          else:
              total -= current_value
          prev_value = current_value
      
      return total