This option allows for transactions that never expire, aka "immortal". By default, a transaction is only valid for approximately 5 minutes (250 blocks) after its construction. Allows for transaction construction to be decoupled from its submission, such as requiring manual approval for the signing or providing "at least once" guarantees.
More information can be found here. Note the Polymesh chain will never reap Accounts, so the risk of a replay attack is mitigated.
BigNumber> | () =>
nonce value for signing the transaction
An Account can directly fetch its current nonce by calling account.getCurrentNonce. More information can be found at: https://polkadot.js.org/docs/api/cookbook/tx/#how-do-i-take-the-pending-tx-pool-into-account-in-my-nonce
the passed value can be either the nonce itself or a function that returns the nonce. This allows, for example, passing a closure that increases the returned value every time it's called, or a function that fetches the nonce from the chain or a different source
Account or address of a signing key to replace the current one (for this procedure only)