read_tlv_fields!(reader, {
(0, session_priv, required),
(1, payment_id, option),
(2, first_hop_htlc_msat, required),
(4, path_hops, vec_type),
(5, payment_params, (option: ReadableArgs, 0)),
read_tlv_fields!(reader, {
(0, session_priv, required),
(1, payment_id, option),
(2, first_hop_htlc_msat, required),
(4, path_hops, vec_type),
(5, payment_params, (option: ReadableArgs, 0)),