Returns and sends a copy of the message to start processing, while
the sender also continues processing.
As this method, other than the similar method
start,
starts a copy of the message, it can be called multiple times with the
same receiving message.
If
target is specified,
the message is sent to
target
and both the receiving message and the message copy are changed to use
the new
target.
Otherwise the message is sent to the target the message object provides.
If any
arguments are specified,
the message is sent with these
arguments
and both the receiving message and the message copy are changed to use
the new
arguments.
Otherwise the message is sent with any arguments the message object provides.
This method returns as soon as possible and does not wait until
message processing is complete.
The
notify
method can be used to request notification that message processing is complete.
When message processing is complete, the message object retains any
result and holds it until requested via the
result method.
