code: def is_in(allowed_values  # type: Set
            ):
      
      def is_in_allowed_values(x):
          if x in allowed_values:
              return True
          else:
              # raise Failure('is_in: x in ' + str(allowed_values) + ' does not hold for x=' + str(x))
              raise NotInAllowedValues(wrong_value=x, allowed_values=allowed_values)
  
      is_in_allowed_values.__name__ = 'is_in_{}'.format(allowed_values)
      return is_in_allowed_values
docs: 'Values in' validation_function generator.
      Returns a validation_function to check that x is in the provided set of allowed values
  
      :param allowed_values: a set of allowed values
      :return: