Check if an an API Gateway REST API exists.

def rest_api_exists(self, rest_api_id):
        # type: (str) -> bool
        """Check if an an API Gateway REST API exists."""
        client = self._client('apigateway')
        try:
            client.get_rest_api(restApiId=rest_api_id)
            return True
        except client.exceptions.NotFoundException:
            return False