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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 halfmax_points(self):
 """Get the bandpass' half-maximum wavelengths. These can be used to compute a representative bandwidth, or for display purposes. Unlike calc_halfmax_points(), this function will use a cached value if available. """

        t = self.registry._halfmaxes.get((self.telescope, self.band))
        if t is not None:
            return t

        t = self.calc_halfmax_points()
        self.registry.register_halfmaxes(self.telescope, self.band, t[0], t[1])
        return t