The user id a wallet account belongs to: the part before its :kind suffix. For
usr_alice:spendable this is usr_alice; for a malformed :spendable (empty user id) it's the
empty string, which the submit pipeline rejects. Only meaningful for the wallet accounts
isWalletAccount identifies. For a session escrow account this returns the
<userId>:<sessionId> prefix, not a user id; use escrowPartsOf for those.
The user id a wallet account belongs to: the part before its
:kindsuffix. Forusr_alice:spendablethis isusr_alice; for a malformed:spendable(empty user id) it's the empty string, which the submit pipeline rejects. Only meaningful for the wallet accounts isWalletAccount identifies. For a session escrow account this returns the<userId>:<sessionId>prefix, not a user id; useescrowPartsOffor those.