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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 reddening(self,extval):
 """Compute the reddening for the given extinction. .. math:: A(V) = R(V) \\; \\times \\; E(B-V) \\textnormal{THRU} = 10^{-0.4 \\; A(V)} .. note:: ``self.litref`` is passed into ``ans.citation``. Parameters extval : float Value of :math:`E(B-V)` in magnitudes. Returns ------- ans : `~pysynphot.spectrum.ArraySpectralElement` Extinction curve to apply to a source spectrum. """

        T = 10.0**(-0.4*extval*self.obscuration)
        ans = ExtinctionSpectralElement(wave=self.wave,
                                        waveunits=self.waveunits,
                                        throughput=T,
                                        name='%s(EBV=%g)'%(self.name, extval))
        ans.citation = self.litref
        return ans