The file name.
The file type.
The file URL.
Session type.
The message extension.
The file object.
The sender, which can only be the current user and can not be changed.
The image height.
Whether the message is a thread message.
Whether read receipts are required during a group session.
The recipient.
The message type.
The file URL. If the file is uploaded, you can directly use the URL.
The image width.
The callback of file upload completion.
The callback of a file upload error.
The callback of the file upload progress.
The message body.