You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: attribution.go
    path of file: ./repos/storj/cmd/satellite/reports
    
    the code of the file until where you have to start completion: // Copyright (C) 2019 Storj Labs, Inc.
// See LICENSE for copying information.

package reports

import (
	"context"
	"encoding/csv"
	"fmt"
	"io"
	"os"
	"strconv"
	"strings"
	"time"

	"github.com/zeebo/errs"
	"go.uber.org/zap"

	"storj.io/common/memory"
	"storj.io/common/useragent"
	"storj.io/common/uuid"
	"storj.io/storj/satellite/attribution"
	"storj.io/storj/satellite/satellitedb"
)

var headers = []string{
	"userAgent",
	"projectID",
	"bucketName",
	"gbHours",
	"segmentHours",
	"objectHours",
	"hours",
	"gbEgress",
}

// AttributionTotals is a map of attribution totals per user agent, project ID, and bucket name combination.
type AttributionTotals map[AttributionTotalsI
    
func GenerateAttributionCSV(ctx context.Context, database string, start time.Time, end time.Time, userAgents []string, output io.Writer) error {
	log := zap.L().Named("attribution-report")
	db, err := satellitedb.Open(ctx, log.Named("db"), database, satellitedb.Options{ApplicationName: "satellite-attribution"})
	if err != nil {
		return errs.New("error connecting to master database on satellite: %+v", err)
	}
	defer func() {
		err = errs.Combine(err, db.Close())
		if err != nil {
			log.Error("Error closing satellite DB connection after retrieving partner value attribution data.", zap.Error(err))
		}
	}()

	rows, err := db.Attribution().QueryAllAttribution(ctx, start, end)
	if err != nil {
		return errs.Wrap(err)
	}

	partnerAttributionTotals := ProcessAttributions(rows, userAgents, log)

	w := csv.NewWriter(output)
	defer func() {
		w.Flush()
	}()

	if err := w.Write(headers); err != nil {
		return errs.Wrap(err)
	}
	for idx, totals := range partnerAttributionTotals {
		gbHours := memory.Size(totals.ByteHours).GB()
		egressGBData := memory.Size(totals.BytesEgress).GB()
		record := []string{
			idx.UserAgent,
			idx.ProjectID,
			idx.BucketName,
			strconv.FormatFloat(gbHours, 'f', 4, 64),
			strconv.FormatFloat(totals.SegmentHours, 'f', 4, 64),
			strconv.FormatFloat(totals.ObjectHours, 'f', 4, 64),
			strconv.FormatFloat(totals.BucketHours, 'f', 4, 64),
			strconv.FormatFloat(egressGBData, 'f', 4, 64),
		}
		if err := w.Write(record); err != nil {
			return errs.Wrap(err)
		}
	}
	if err := w.Error(); err != nil {
		return errs.Wrap(err)
	}

	if output != os.Stdout {
		fmt.Println("Generated report for partner attribution")
	}
	return errs.Wrap(err)
}