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: convert_vols.m
    path of file: ./repos/bspm/thirdparty/spm12/toolbox/marsbar-0.44/@mardo_5
    
    the code of the file until where you have to start completion: function o = convert_vols(o, ver)
% method that converts vol structs in design and converts to format 'ver'
% FORMAT o = convert_fo(o, ver)
% 
% Input
% o        - design object
% ver      - optional version for vols from '99' or '5'
%            Defaults to version for current SPM version
%
% Output
% o        - object with converted vols
% 

    
function o = convert_vols(o, ver)
% method that converts vol structs in design and converts to format 'ver'
% FORMAT o = convert_fo(o, ver)
% 
% Input
% o        - design object
% ver      - optional version for vols from '99' or '5'
%            Defaults to version for current SPM version
%
% Output
% o        - object with converted vols
% 
% Example
% % Convert vols to current format
% o = convert_vols(o);
% 
% % Convert to native format for SPM99 designs
% o = convert_vols(o, native_vol_ver(o));
% 
% $Id$

if nargin < 2
  ver = mars_vol_utils('current_ver');
end