calculates current usage for all DynamoDB limits

def _find_usage_dynamodb(self):
        """calculates current usage for all DynamoDB limits"""
        table_count = 0
        region_read_capacity = 0
        region_write_capacity = 0

        logger.debug("Getting usage for DynamoDB tables")
        for table in self.resource_conn.tables.all():
            table_count += 1
            gsi_write = 0
            gsi_read = 0
            gsi_count = 0
            if table.global_secondary_indexes is not None:
                for gsi in table.global_secondary_indexes:
                    gsi_count += 1
                    gsi_read += gsi['ProvisionedThroughput'][
                        'ReadCapacityUnits']
                    gsi_write += gsi['ProvisionedThroughput'][
                        'WriteCapacityUnits']
            table_write_capacity = table.provisioned_throughput[
                                       'WriteCapacityUnits'] + gsi_write
            table_read_capacity = table.provisioned_throughput[
                                      'ReadCapacityUnits'] + gsi_read
            region_write_capacity += table_write_capacity
            region_read_capacity += table_read_capacity

            self.limits['Global Secondary Indexes']._add_current_usage(
                gsi_count,
                resource_id=table.name,
                aws_type='AWS::DynamoDB::Table'
            )

            self.limits['Local Secondary Indexes']._add_current_usage(
                len(table.local_secondary_indexes)
                if table.local_secondary_indexes is not None else 0,
                resource_id=table.name,
                aws_type='AWS::DynamoDB::Table'
            )

            self.limits['Table Max Write Capacity Units']._add_current_usage(
                table_write_capacity,
                resource_id=table.name,
                aws_type='AWS::DynamoDB::Table'
            )

            self.limits['Table Max Read Capacity Units']._add_current_usage(
                table_read_capacity,
                resource_id=table.name,
                aws_type='AWS::DynamoDB::Table'
            )

        self.limits['Tables Per Region']._add_current_usage(
            table_count,
            aws_type='AWS::DynamoDB::Table'
        )

        self.limits['Account Max Write Capacity Units']._add_current_usage(
            region_write_capacity,
            aws_type='AWS::DynamoDB::Table'
        )

        self.limits['Account Max Read Capacity Units']._add_current_usage(
            region_read_capacity,
            aws_type='AWS::DynamoDB::Table'
        )