func (p *persistence) tempFileNameForFingerprint(fp model.Fingerprint) string {
	fpStr := fp.String()
	return filepath.Join(p.basePath, fpStr[0:seriesDirNameLen], fpStr[seriesDirNameLen:]+seriesTempFileSuffix)
}
func (p *persistence) dirNameForFingerprint(fp model.Fingerprint) string {
	fpStr := fp.String()
	return filepath.Join(p.basePath, fpStr[0:seriesDirNameLen])
}