code: def set_illuminant(self, illuminant):
          
          illuminant = illuminant.lower()
          if illuminant not in color_constants.ILLUMINANTS[self.observer]:
              raise InvalidIlluminantError(illuminant)
          self.illuminant = illuminant
docs: Validates and sets the color's illuminant.
  
          .. note:: This only changes the illuminant. It does no conversion
              of the color's coordinates. For this, you'll want to refer to
              :py:meth:`XYZColor.apply_adaptation <colormath.color_objects.XYZColor.apply_adaptation>`.
  
          .. tip:: Call this after setting your observer.
  
          :param str illuminant: One of the various illuminants.