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: voc0712_trainval_ss.m
    path of file: ./repos/R-FCN/experiments/+Dataset
    
    the code of the file until where you have to start completion: function dataset = voc0712_trainval_ss(dataset, usage, use_flip)
% Pascal voc 0712 trainval set with selective search
% set opts.imdb_train opts.roidb_train 
% or set opts.imdb_test opts.roidb_train


    
function dataset = voc0712_trainval_ss(dataset, usage, use_flip)
% Pascal voc 0712 trainval set with selective search
% set opts.imdb_train opts.roidb_train 
% or set opts.imdb_test opts.roidb_train

% change to point to your devkit install
devkit2007                      = voc2007_devkit();
devkit2012                      = voc2012_devkit();

switch usage
    case {'train'}
        dataset.imdb_train    = {  imdb_from_voc(devkit2007, 'trainval', '2007', use_flip), ...
                                    imdb_from_voc(devkit2012, 'trainval', '2012', use_flip)};
        dataset.roidb_train   = cellfun(@(x) x.roidb_func(x, 'with_selective_search', true), dataset.imdb_train, 'UniformOutput', false);
    case {'test'}
        error('only supports one source test currently');  
    otherwise
        error('usage = ''train'' or ''test''');
end