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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 _num_vowel_to_acc(vowel, tone):
 """Convert a numbered vowel to an accented vowel."""

    try:
        return VOWEL_MAP[vowel + str(tone)]
    except IndexError:
        raise ValueError("Vowel must be one of '{}' and tone must be a tone.".format(VOWELS))