docs: def update_fixed(self, kwargs_lens, kwargs_source, kwargs_lens_light, kwargs_ps, kwargs_cosmo, lens_add_fixed=[],
                       source_add_fixed=[], lens_light_add_fixed=[], ps_add_fixed=[], cosmo_add_fixed=[], lens_remove_fixed=[],
                       source_remove_fixed=[], lens_light_remove_fixed=[], ps_remove_fixed=[], cosmo_remove_fixed=[]):
          """
          adds the values of the keyword arguments that are stated in the _add_fixed to the existing fixed arguments.
  
          :param kwargs_lens:
          :param kwargs_source:
          :param kwargs_lens_light:
          :param kwargs_ps:
          :param kwargs_cosmo:
          :param lens_add_fixed:
          :param source_add_fixed:
          :param lens_light_add_fixed:
          :param ps_add_fixed:
          :param cosmo_add_fixed:
          :return: updated kwargs fixed
          """
          lens_fixed = self._add_fixed(kwargs_lens, self._lens_fixed, lens_add_fixed)
          lens_fixed = self._remove_fixed(lens_fixed, lens_remove_fixed)
          source_fixed = self._add_fixed(kwargs_source, self._source_fixed, source_add_fixed)
          source_fixed = self._remove_fixed(source_fixed, source_remove_fixed)
          lens_light_fixed = self._add_fixed(kwargs_lens_light, self._lens_light_fixed, lens_light_add_fixed)
          lens_light_fixed = self._remove_fixed(lens_light_fixed, lens_light_remove_fixed)
          ps_fixed = self._add_fixed(kwargs_ps, self._ps_fixed, ps_add_fixed)
          ps_fixed = self._remove_fixed(ps_fixed, ps_remove_fixed)
          cosmo_fixed = copy.deepcopy(self._cosmo_fixed)
          for param_name in cosmo_add_fixed:
              if param_name in cosmo_fixed:
                  pass
              else:
                  cosmo_fixed[param_name] = kwargs_cosmo[param_name]
          for param_name in cosmo_remove_fixed:
              if param_name in cosmo_fixed:
                  del cosmo_fixed[param_name]
                  self._lens_fixed, self._source_fixed, self._lens_light_fixed, self._ps_fixed, self._cosmo_fixed = lens_fixed, source_fixed, lens_light_fixed, ps_fixed, cosmo_fixed