def update_lun(self, add_luns=None, remove_luns=None):
if not add_luns and not remove_luns:<EOL><INDENT>log.debug("<STR_LIT>"<EOL>"<STR_LIT>")<EOL>return RESP_OK<EOL><DEDENT>lun_add = self._prepare_luns_add(add_luns)<EOL>lun_remove = self._prepare_luns_remove(remove_luns, True)<EOL>return self.modify(lun_add=lun_add, lun_remove=lun_remove)<EOL>
Updates the LUNs in CG, adding the ones in `add_luns` and removing
        the ones in `remove_luns`