code: def efficiency(self, wavelengths=None):
          
          x = self._validate_wavelengths(wavelengths).value
          y = self(x).value
          qtlam = abs(np.trapz(y / x, x=x))
          return qtlam * u.dimensionless_unscaled
docs: Calculate :ref:`dimensionless efficiency <synphot-formula-qtlam>`.
  
          Parameters
          ----------
          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
          -------
          qtlam : `~astropy.units.quantity.Quantity`
              Dimensionless efficiency.