Optional attributes returned
Note that some attributes are returned in the payload only under specific conditions:
sharedMessageonly when the message represented by this class is a wall post sharing another message;
replacingonly when the corresponding message is sent as an update to another message thanks to Update Message endpoint. Note that the first two attributes relate to the original (and therefore first) message sent, whereas the
replacingattribute relates to the message that has been updated by this message;
replacedByonly when this message has been updated by a new message. It contains the id of the replacing message.
parentMessageIdonly when this message is a reply or a forward of another message which id is returned in this attribute.