A question about the certificate file


I generated a certificate and it’s verified correctly.
I noticed the signature’s Merkle proof is empty(shown below) in the certificate file.
so I want to ask how to get proof value and write it in the certificate file.

“signature”: {
“type”: [
“merkleRoot”: “35c182e6c58d686283264d8e422cf16b76b4b87ce099286037c5e43528190ee5”,
“targetHash”: “35c182e6c58d686283264d8e422cf16b76b4b87ce099286037c5e43528190ee5”,
“proof”: [],
“anchors”: [
“sourceId”: “0xf40e468c2cd6a7bdeacacb4e26a89ac49fcd927a4aba16825e63c5b74074f963”,
“type”: “ETHData”,
“chain”: “ethereumRopsten”

I believe the proof is supposed to be empty unless it’s issued with a batch of certificates. In this case, the target hash is the merkle root, so there’s no need to traverse the “proof” which would consist of a series of Left:, Right: statements that let one find the hash given the merkleRoot