Message.EvSourceMessage events.
The type for MessageEvent and ExtendableMessageEvent objects.
as_extendable e is e as an extendable event. Warning. only for ExtendableMessageEvents objects.
data e is the data send by the emitter. Warning. Unsafe, make sure to constrain the result value to the right type.
source e is the message emitter.
ports e is a list of ports associated with the channel the message is being send through (if applicable).
message is the message event.
messageerror is the messageerror event.