*priority*.
Executing the event means executing ``action(*argument, **kwargs)``.
- Optional *argument* argument must be a sequence holding the parameters
- for *action* if any used.
- Optional *kwargs* argument must be a dictionary holding the keyword
- parameters for *action* if any used.
+ *argument* is a sequence holding the positional arguments for *action*.
+ *kwargs* is a dictionary holding the keyword arguments for *action*.
Return value is an event which may be used for later cancellation of the event
(see :meth:`cancel`).