If incoming, the author that sent the message, if the message was sent in a channel. If outgoing, undefined.
The contact that sent or received the message.
The duration of the voice message in milliseconds.
The unique identifier of the message. This can be used to lookup messages in the history. This identifier persists across sessions.
Whether the message was received or sent.
The timestamp of the message.
A Zello history voice message. To play the message, use the Zello#playHistoryMessage function.