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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 max_order(self):
 """ Depth of the smallest HEALPix cells found in the MOC instance. """

        # TODO: cache value
        combo = int(0)
        for iv in self._interval_set._intervals:
            combo |= iv[0] | iv[1]

        ret = AbstractMOC.HPY_MAX_NORDER - (utils.number_trailing_zeros(combo) // 2)
        if ret < 0:
            ret = 0

        return ret