code: def wave(self, wavelength):
          
          # 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
docs: A setter for the wavelength
  
          Parameters
          ----------
          wavelength: astropy.units.quantity.Quantity
              The array with units