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: xmlStyle.go
    path of file: ./repos/go-gin-example/vendor/github.com/tealeg/xlsx
    
    the code of the file until where you have to start completion: // xslx is a package designed to help with reading data from
// spreadsheets stored in the XLSX format used in recent versions of
// Microsoft's Excel spreadsheet.
//
// For a concise example of how to use this library why not check out
// the source for xlsx2csv here: https://github.com/tealeg/xlsx2csv

package xlsx

import (
	"bytes"
	"encoding/xml"
	"fmt"
	"strconv"
	"sync"
)

// Excel styles can reference number formats that are built-in, all of which
// have an id less than 164.
const builtinNumFmtsCount = 163

// Excel styles can reference number formats that are built-in, all of which
// have an id less than 164. This is a possibly incomplete list comprised of as
// many of them as I could find.
var builtInNumFmt = map[int]string{
	0:  "general",
	1:  "0",
	2:  "0.00",
	3:  "#,##0",
	4:  "#,##0.00",
	9:  "0%",
	10: "0.00%",
	11: "0.00e+00",
	12: "# ?/?",
	13: "# ??/??",
	14: "mm-dd-yy",
	15: "d-mmm-yy",
	16: "d-mmm",
	17: "mmm-yy",
	18: "h:mm am/pm",
	19: "h:mm:ss am/pm",
	20: "h:mm",
	21: "h:mm:ss",
	22: "m/d/yy h:mm",
	37: "#,##0 ;(#,##0)",
	38: "#,##0 ;[red](#,##0)",
	39: "#,##0.00;(#,##0.00)",
	40: "#,##0.00
    
func (styles *xlsxStyleSheet) Marshal() (string, error) {
	result := xml.Header + `<styleSheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">`

	xNumFmts, err := styles.NumFmts.Marshal()
	if err != nil {
		return "", err
	}
	result += xNumFmts

	outputFontMap := make(map[int]int)
	xfonts, err := styles.Fonts.Marshal(outputFontMap)
	if err != nil {
		return "", err
	}
	result += xfonts

	outputFillMap := make(map[int]int)
	xfills, err := styles.Fills.Marshal(outputFillMap)
	if err != nil {
		return "", err
	}
	result += xfills

	outputBorderMap := make(map[int]int)
	xborders, err := styles.Borders.Marshal(outputBorderMap)
	if err != nil {
		return "", err
	}
	result += xborders

	if styles.CellStyleXfs != nil {
		xcellStyleXfs, err := styles.CellStyleXfs.Marshal(outputBorderMap, outputFillMap, outputFontMap)
		if err != nil {
			return "", err
		}
		result += xcellStyleXfs
	}

	xcellXfs, err := styles.CellXfs.Marshal(outputBorderMap, outputFillMap, outputFontMap)
	if err != nil {
		return "", err
	}
	result += xcellXfs

	if styles.CellStyles != nil {
		xcellStyles, err := styles.CellStyles.Marshal()
		if err != nil {
			return "", err
		}
		result += xcellStyles
	}

	return result + "</styleSheet>", nil
}