code: def sort_vid_split(vs):
      
      match = var_re.match(vs)
      if match is None:
          raise ValueError('Invalid variable string: {}'.format(str(vs)))
      else:
          return match.groups()
docs: Split a valid variable string into its variable sort and id.
  
      Examples:
          >>> sort_vid_split('h3')
          ('h', '3')
          >>> sort_vid_split('ref-ind12')
          ('ref-ind', '12')