### index(): long
Returns the index of a `MilestonePayloadEssence`.
### timestamp(): long
Returns the timestamp of a `MilestonePayloadEssence`.
### parents(): [MessageId[]](#messageid)
Returns the parents of a `MilestonePayloadEssence`.
### merkleProof(): byte[]
Returns the merkle proof of a `MilestonePayloadEssence`.
### nextPowScore(): long
Returns the next proof of work score of a `MilestonePayloadEssence`.
### nextPowScoreMilestone(): long
Returns the next proof of work index of a `MilestonePayloadEssence`.
### publicKeys(): [PublicKey[]](#publickey)
Returns the public keys of a `MilestonePayloadEssence`.
### receipt(): Optional<[ReceiptPayload](#receiptpayload)>
Returns the optional receipt of a `MilestonePayloadEssence`.
### hash(): byte[]
Hashes the `MilestonePayloadEssence to be signed.`