A setter for the wavelength

        Parameters
        ----------
        wavelength: astropy.units.quantity.Quantity
            The array with units

def wave(self, wavelength):
        """A setter for the wavelength

        Parameters
        ----------
        wavelength: astropy.units.quantity.Quantity
            The array with units
        """
        # Test units
        if not isinstance(wavelength, q.quantity.Quantity):
            raise ValueError("Wavelength must be in length units.")

        self._wave = wavelength
        self.wave_units = wavelength.unit