code: func (sf *StreamFile) Close() error {
  	if sf.err != nil {
  		return sf.err
  	}
  	// If there are sheets that have not been written yet, call NextSheet() which will add files to the zip for them.
  	// XLSX readers may error if the sheets registered in the metadata are not present in the file.
  	if sf.currentSheet != nil {
  		for sf.currentSheet.index < len(sf.xlsxFile.Sheets) {
  			if err := sf.NextSheet(); err != nil {
  				sf.err = err
  				return err
  			}
  		}
  		// Write the end of the last sheet.
  		if err := sf.writeSheetEnd(); err != nil {
  			sf.err = err
  			return err
  		}
  	}
  	err := sf.zipWriter.Close()
  	if err != nil {
  		sf.err = err
  	}
  	return err
  }
docs: // Close closes the Stream File.
  // Any sheets that have not yet been written to will have an empty sheet created for them.