func (k Keys) ApplyToHeader(h *lob.Header) {
for csid, v := range k {
h.Set(hex.EncodeToString([]byte{csid}), v.String())
}
}
func (p Parts) ApplyToHeader(h *lob.Header) {
for k, v := range p {
h.Set(hex.EncodeToString([]byte{k}), v)
}
}