Returns the Lambda Permission resource allowing SNS to invoke the function this event source triggers.

        :param dict kwargs: no existing resources need to be modified
        :returns: a list of vanilla CloudFormation Resources, to which this SNS event expands
        :rtype: list

def to_cloudformation(self, **kwargs):
        """Returns the Lambda Permission resource allowing SNS to invoke the function this event source triggers.

        :param dict kwargs: no existing resources need to be modified
        :returns: a list of vanilla CloudFormation Resources, to which this SNS event expands
        :rtype: list
        """
        function = kwargs.get('function')

        if not function:
            raise TypeError("Missing required keyword argument: function")

        return [self._construct_permission(function, source_arn=self.Topic),
                self._inject_subscription(function, self.Topic, self.FilterPolicy)]