Return a dictionary of variables with `type` :class:`CFNType`.

        Returns:
            dict: variables that need to be submitted as CloudFormation
                Parameters.

def get_cfn_parameters(self):
        """Return a dictionary of variables with `type` :class:`CFNType`.

        Returns:
            dict: variables that need to be submitted as CloudFormation
                Parameters.

        """
        variables = self.get_variables()
        output = {}
        for key, value in variables.items():
            if hasattr(value, "to_parameter_value"):
                output[key] = value.to_parameter_value()
        return output