def METHOD_NAME(wp):
  if wp.data == []:
    raise Sorry("need one or more data directories")
  #handle globs at this level:
  import glob
  provisional = []
  for glob_item in wp.data:
    provisional = provisional + glob.glob(glob_item)
  wp.data = provisional
  for item in wp.data:
    if not os.path.isdir(item):
      raise Sorry("can't stat directory",item)
  if wp.bravais_setting_id is None or \
     wp.bravais_setting_id not in [1,2,5,9,12,22]:
    raise Sorry("""must set the bravais_setting_id
  triclinic=1 monoclinic=2 orthorhombic=5 rhombohedral=5
  tetragonal=9 hexagonal=12 cubic=22""")