You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: symmetrise.m
    path of file: ./repos/mtex/geometry/@slipSystem
    
    the code of the file until where you have to start completion: function [sS,id] = symmetrise(sS,varargin)
% find all symmetrically equivalent slips systems
%
% Syntax

    
function [sS,id] = symmetrise(sS,varargin)
% find all symmetrically equivalent slips systems
%
% Syntax
%
%   sSAll = sS.symmetrise
%   [sSAll,id] = symmetrise(sS)
%
% Input
%  sS - @slipSystem
%
% Output
%  sSAll - @slipSystem
%  id    - id of the slipSystem before symmetrisation
%

if ~isa(sS.b,'Miller'), return; end