code: def is_option(value, *options):
      
      if not isinstance(value, string_types):
          raise VdtTypeError(value)
      if not value in options:
          raise VdtValueError(value)
      return value
docs: This check matches the value to any of a set of options.
  
      >>> vtor = Validator()
      >>> vtor.check('option("yoda", "jedi")', 'yoda')
      'yoda'
      >>> vtor.check('option("yoda", "jedi")', 'jed')  # doctest: +SKIP
      Traceback (most recent call last):
      VdtValueError: the value "jed" is unacceptable.
      >>> vtor.check('option("yoda", "jedi")', 0)  # doctest: +SKIP
      Traceback (most recent call last):
      VdtTypeError: the value "0" is of the wrong type.