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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 extinction_curve(self, ebv, wavelengths=None):
 """Generate extinction curve. .. math:: A(V) = R(V) \\; \\times \\; E(B-V) THRU = 10^{-0.4 \\; A(V)} Parameters ebv : float or `~astropy.units.quantity.Quantity` :math:`E(B-V)` value in magnitude. wavelengths : array-like, `~astropy.units.quantity.Quantity`, or `None` Wavelength values for sampling. If not a Quantity, assumed to be in Angstrom. If `None`, ``self.waveset`` is used. Returns ------- extcurve : `ExtinctionCurve` Empirical extinction curve. Raises ------ synphot.exceptions.SynphotError Invalid input. """

        if isinstance(ebv, u.Quantity) and ebv.unit.decompose() == u.mag:
            ebv = ebv.value
        elif not isinstance(ebv, numbers.Real):
            raise exceptions.SynphotError('E(B-V)={0} is invalid.'.format(ebv))

        x = self._validate_wavelengths(wavelengths).value
        y = 10 ** (-0.4 * self(x).value * ebv)
        header = {
            'E(B-V)': ebv,
            'ReddeningLaw': self.meta.get('expr', 'unknown')}

        return ExtinctionCurve(ExtinctionModel1D, points=x, lookup_table=y,
                               meta={'header': header})