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: cnn_imagenet_setup_data.m
    path of file: ./repos/2015_Face_Detection/examples
    
    the code of the file until where you have to start completion: function imdb = cnn_imagenet_setup_data(varargin)
% CNN_IMAGENET_SETUP_DATA  Initialize ImageNet ILSVRC CLS-LOC challenge data
%    This function creates an IMDB structure pointing to a local copy
%    of the ILSVRC CLS-LOC data.
%
%    The ILSVRC data ships in several TAR archives that can be
%    obtained from the ILSVRC challenge website. You will need:
%
%    ILSVRC2012_img_train.tar
%    ILSVRC2012_img_val.tar
%    ILSVRC2012_img_test.tar
%    ILSVRC2012_devkit.tar
%
%    Note that images in the CLS-LOC challenge are the same for the 2012, 2013,
%    and 2014 edition of ILSVRC, but that the development kit
%    is different. However, all devkit versions should work.
%
%    In order to use the ILSVRC data with these scripts, please

    
function imdb = cnn_imagenet_setup_data(varargin)
% CNN_IMAGENET_SETUP_DATA  Initialize ImageNet ILSVRC CLS-LOC challenge data
%    This function creates an IMDB structure pointing to a local copy
%    of the ILSVRC CLS-LOC data.
%
%    The ILSVRC data ships in several TAR archives that can be
%    obtained from the ILSVRC challenge website. You will need:
%
%    ILSVRC2012_img_train.tar
%    ILSVRC2012_img_val.tar
%    ILSVRC2012_img_test.tar
%    ILSVRC2012_devkit.tar
%
%    Note that images in the CLS-LOC challenge are the same for the 2012, 2013,
%    and 2014 edition of ILSVRC, but that the development kit
%    is different. However, all devkit versions should work.
%
%    In order to use the ILSVRC data with these scripts, please
%    unpack it as follows. Create a root folder <DATA>, by default
%
%    data/imagenet12
%
%    (note that this can be a simlink). Use the 'dataDir' option to
%    specify a different path.
%
%    Within this folder, create the following hierarchy:
%
%    <DATA>/images/train/ : content of ILSVRC2012_img_train.tar
%    <DATA>/images/val/ : content of ILSVRC2012_img_val.tar
%    <DATA>/images/test/ : content of ILSVRC2012_img_test.tar
%    <DATA>/ILSVRC2012_devkit : content of ILSVRC2012_devkit.tar
%
%    In order to speedup training and testing, it may be a good idea
%    to preprocess the images to have a fixed size (e.g. 256 pixels
%    high) and/or to store the images in RAM disk (provided that
%    sufficient RAM is available). Reading images off disk with a
%    sufficient speed is crucial for fast training.

opts.dataDir = fullfile('data','imagenet12') ;
opts.lite = false ;
opts = vl_argparse(opts, varargin) ;

% -------------------------------------------------------------------------
%                                                  Load categories metadata
% -------------------------------------------------------------------------

d = dir(fullfile(opts.dataDir, '*devkit*')) ;
if numel(d) == 0
  error('Make sure that ILSVRC data is correctly installed in %s', ...
    opts.dataDir) ;
end