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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 _min_depth(self):
 """Finds minimum path length from the root. Notes ----- Internal method. Do not call directly. Returns ------- int Minimum path length from the root. """

        if "min_depth" in self.__dict__:
            return self.__dict__["min_depth"]

        min_depth = 0
        hypernyms = self.hypernyms()
        if hypernyms:
            min_depth = 1 + min(h._min_depth() for h in hypernyms)
        self.__dict__["min_depth"] = min_depth

        return min_depth