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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 longest_one_seg_prefix(self, word):
 """Return longest IPA Unicode prefix of `word` Args: word (unicode):
 word as IPA string Returns: unicode: longest single-segment prefix of `word` """

        match = self.seg_regex.match(word)
        if match:
            return match.group(0)
        else:
            return ''