def METHOD_NAME(self, x_pos, y_pos, kwargs_lens, kwargs_special):
    """
    :param kwargs_lens: lens model keyword argument list
    :param kwargs_special: dictionary of 'special' keyword parameters
    :return: log likelihood of the measured flux ratios given a model
    """
    if self._source_type == "INF":
        mag = np.abs(
            self._lens_model_class.magnification(x_pos, y_pos, kwargs_lens)
        )
    else:
        source_sigma = kwargs_special["source_size"]
        mag = self._lens_model_extensions.magnification_finite(
            x_pos,
            y_pos,
            kwargs_lens,
            source_sigma=source_sigma,
            window_size=self._window_size,
            grid_number=self._gird_number,
            polar_grid=self._polar_grid,
            aspect_ratio=self._aspect_ratio,
        )
    if len(mag) - 1 != len(self._flux_ratios):
        return -(10**15)
    mag_ratio = mag[1:] / mag[0]
    return self._logL(mag_ratio)