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: xmlWorksheet.go
    path of file: ./repos/xorm/vendor/github.com/tealeg/xlsx
    
    the code of the file until where you have to start completion: package xlsx

import (
	"encoding/xml"
	"strings"
)

// xlsxWorksheet directly maps the worksheet element in the namespace
// http://schemas.openxmlformats.org/spreadsheetml/2006/main -
// currently I have not checked it for completeness - it does as much
// as I need.
type xlsxWorksheet struct {
	XMLName       xml.Name          `xml:"http://schemas.openxmlformats.org/spreadsheetml/2006/main worksheet"`
	SheetPr   
    
func (mc *xlsxMergeCells) getExtent(cellRef string) (int, int, error) {
	if mc == nil {
		return 0, 0, nil
	}
	for _, cell := range mc.Cells {
		if strings.HasPrefix(cell.Ref, cellRef+":") {
			parts := strings.Split(cell.Ref, ":")
			startx, starty, err := GetCoordsFromCellIDString(parts[0])
			if err != nil {
				return -1, -1, err
			}
			endx, endy, err := GetCoordsFromCellIDString(parts[1])
			if err != nil {
				return -2, -2, err
			}
			return endx - startx, endy - starty, nil
		}
	}
	return 0, 0, nil
}