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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 pos(self):
 """ Lazy-loads the part of speech tag for this word :getter: Returns the plain string value of the POS tag for the word :type: str """

        if self._pos is None:
            poses = self._element.xpath('POS/text()')
            if len(poses) > 0:
                self._pos = poses[0]
        return self._pos