docs: def fetch_from_sdr(folder=data_folder, data='test'):
      """
      Download MRS data from SDR
  
      Parameters
      ----------
      folder : str
          Full path to a location in which to place the data. Per default this
      will be a directory under the user's home `.mrs_data`.
  
      data : str
         Which data to download. Either 'test', which is data required for
         testing, or 'example', which is data needed for the example notebooks.
         
      """
      url = "https://stacks.stanford.edu/file/druid:fn662rv4961/"
  
      if data == 'test':
          md5_dict = {'5182_1_1.nii.gz': '0656e59818538baa7d45311f2581bb4e',
                  '5182_15_1.nii.gz': 'a5a307b581620184baf868cd0df81f89',
                  'data.mat': 'a6275698f2220c65994354d412e6d82e',
                  'pure_gaba_P64024.nii.gz': 'f3e09ec0f00bd9a03910b19bfe731afb'}
  
      elif data == 'example':
          md5_dict = {'12_1_PROBE_MEGA_L_Occ.nii.gz':
                      'a0571606c1caa16a9d9b00847771bc94',
                       '5062_2_1.nii.gz':
                      '6f77fb5134bc2841bdfc954390f0f4a4'}
          
      if not os.path.exists(folder):
          print('Creating new directory %s' % folder)
          os.makedirs(folder)
          
      for k, v in md5_dict.items():
          fname = pjoin(folder, k)
          if not os.path.exists(fname):
              print('Downloading %s from SDR ...'%k)
              _get_file_data(fname, url + k)
              check_md5(fname, v)
          else:
              print('File %s is already in place. If you want to fetch it again, please first remove it from the folder %s ' % (fname, folder))
  
      print('Done.')
      print('Files copied in folder %s' % folder)