Determine the current usage for each limit of this service,
        and update corresponding Limit via
        :py:meth:`~.AwsLimit._add_current_usage`.

def find_usage(self):
        """
        Determine the current usage for each limit of this service,
        and update corresponding Limit via
        :py:meth:`~.AwsLimit._add_current_usage`.
        """
        ignore_statuses = [
            'DELETE_COMPLETE'
        ]
        logger.debug("Checking usage for service %s", self.service_name)
        self.connect()
        for lim in self.limits.values():
            lim._reset_usage()
        count = 0
        paginator = self.conn.get_paginator('describe_stacks')
        iter = paginator.paginate()
        for page in iter:
            for stk in page['Stacks']:
                if stk['StackStatus'] not in ignore_statuses:
                    count += 1
        self.limits['Stacks']._add_current_usage(
            count, aws_type='AWS::CloudFormation::Stack'
        )
        self._have_usage = True
        logger.debug("Done checking usage.")