text: '''
  A format checker that checks that variable length driver formats are parseable.
  Specifically, variable length formats need to be the last specified format in
  the format list, or else consumers won't be able to tell one format from
  another.
  '''
  
  import jsonschema
  
  
  FORMAT_NAME = 'varlen-fmt'
  
  
  def check(fmt_list):
      '''Returns True if the format list has no variable length formats other
      than possibly the last format in the list. Raises FormatError otherwise.'''
  
      for i, fmt in enumerate(fmt_list):
          try:
              size = fmt['size']
          except KeyError:
              continue
  
          if size == 0 and i != len(fmt_list)-1:
              raise jsonschema.exceptions.FormatError(
      '''\
      variable-length (size 0) property must be the last format
      specified but is not
      fmt: %s''' % fmt)
  
      return True
  