thing.update(xxx)is called, the watcher will output
"New value is xxx".
...- The list of event name strings supported by the watcher.
type- The event type to notify. Must be one of the supported events.
...- These parameters are passed directly to the event watcher functions.
id- The unique ID returned from
trueif a watcher with the specified ID exists and was successfully removed.
events- A table of functions, one for each event to watch.
unwatchto stop watching.