def _accented_vowel_to_numbered(vowel):
for numbered_vowel, accented_vowel in _PINYIN_TONES.items():<EOL><INDENT>if vowel == accented_vowel:<EOL><INDENT>return tuple(numbered_vowel)<EOL><DEDENT><DEDENT>
Convert an accented Pinyin vowel to a numbered Pinyin vowel.