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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 apply_raw_r_assimilation(last_syllable: str) -> str: """ -r preceded by an -s-, -l- or -n- becomes respectively en -s, -l or -n. 'armr' 'áss' 'stóll' 'steinn' 'vinn' :param last_syllable: last syllable of an Old Norse word :return: """


    if len(last_syllable) > 0:
        if last_syllable[-1] == "l":
            return last_syllable + "l"
        elif last_syllable[-1] == "s":
            return last_syllable + "s"
        elif last_syllable[-1] == "n":
            return last_syllable + "n"
    return last_syllable + "r"