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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def roman_to_int(roman_string):
 """ Converts a string of roman numbers into an integer. .. code: python reusables.roman_to_int("XXXVI") # 36 :param roman_string: XVI or similar :return: parsed integer """

    roman_string = roman_string.upper().strip()
    if "IIII" in roman_string:
        raise ValueError("Malformed roman string")
    value = 0
    skip_one = False
    last_number = None
    for i, letter in enumerate(roman_string):
        if letter not in _roman_dict:
            raise ValueError("Malformed roman string")
        if skip_one:
            skip_one = False
            continue
        if i < (len(roman_string) - 1):
            double_check = letter + roman_string[i + 1]
            if double_check in _roman_dict:
                if last_number and _roman_dict[double_check] > last_number:
                    raise ValueError("Malformed roman string")
                last_number = _roman_dict[double_check]
                value += _roman_dict[double_check]
                skip_one = True
                continue
        if last_number and _roman_dict[letter] > last_number:
            raise ValueError("Malformed roman string")
        last_number = _roman_dict[letter]
        value += _roman_dict[letter]
    return value