code: def get_freesurfer_dir(directory):
      
      dir_files = [f for f in os.listdir(directory)]
      # Look for sub-folders 'surf' and 'mri'
      if 'surf' in dir_files and 'mri' in dir_files:
          return directory
      # Directory is not a valid freesurfer directory. Continue to search
      # recursively until a matching directory is found.
      for f in os.listdir(directory):
          sub_dir = os.path.join(directory, f)
          if os.path.isdir(sub_dir):
              if get_freesurfer_dir(sub_dir):
                  return sub_dir
      # The given directory does not contain a freesurfer anatomy directory
      return None
docs: Find a subfolder in the given directory that contains a Freesurfer
      anatomy (this may be the directory itself). Currently, the test is whether
      there are sub-folders with name 'surf' and 'mri'. Processes all sub-folders
      recursively until a freesurfer directory is found. If no matching folder is
      found the result is None.
  
      Parameters
      ----------
      directory : string
          Directory on local disk containing unpacked files
  
      Returns
      -------
      string
          Sub-directory containing a Freesurfer files or None if no such
          directory is found.