//
// As a by-product of checking the fields, this function returns paxHdrs, which
// contain all fields that could not be directly encoded.
// A value receiver ensures that this method does not mutate the source Header.
func (h Header) allowedFormats() (format Format, paxHdrs map[string]string, err error) {
	format = FormatUSTAR | FormatPAX | FormatGNU
	paxHdrs = make(map[string]string)

	var whyNoUSTAR, whyNoPAX, whyNoGNU string

			dir, file := path.Split(realName)
			hdr.Name = path.Join(dir, "GNUSparseFile.0", file)
			paxHdrs[paxGNUSparseMajor] = "1"
			paxHdrs[paxGNUSparseMinor] = "0"
			paxHdrs[paxGNUSparseName] = realName
			paxHdrs[paxGNUSparseRealSize] = strconv.FormatInt(realSize, 10)
			paxHdrs[paxSize] = strconv.FormatInt(hdr.Size, 10)
			delete(paxHdrs, paxPath) // Recorded by paxGNUSparseName
		}
	*/
	_ = realSize