Macro send 

macro_rules! send {
    ($($tokens:tt)*) => { ... };
}

Sends a method call to be executed by the actor.

send!(addr.method(arg1, arg2))

Constraints:

• The method must be an inherent method or trait method callable on the actor type.
• The method must take &mut self as the receiver.
• The method must return a future, with an output that implements IntoActorResult.
• The arguments must be Send + 'static.