def set_event_handler(self, eventHandler):
        """
        Set the event handler.

        @warn: This is normally not needed. Use with care!

        @type  eventHandler: L{EventHandler}
        @param eventHandler: New event handler object, or C{None}.

        @rtype:  L{EventHandler}
        @return: Previous event handler object, or C{None}.

        @raise TypeError: The event handler is of an incorrect type.

        @note: The L{eventHandler} parameter may be any callable Python object
            (for example a function, or an instance method).
            However you'll probably find it more convenient to use an instance
            of a subclass of L{EventHandler} here.
        """
        if eventHandler is not None and not callable(eventHandler):
            raise TypeError("Event handler must be a callable object")
        try:
            wrong_type = issubclass(eventHandler, EventHandler)
        except TypeError:
            wrong_type = False
        if wrong_type:
            classname = str(eventHandler)
            msg  = "Event handler must be an instance of class %s"
            msg += "rather than the %s class itself. (Missing parens?)"
            msg  = msg % (classname, classname)
            raise TypeError(msg)
        try:
            previous = self.__eventHandler
        except AttributeError:
            previous = None
        self.__eventHandler = eventHandler
        return previous
Set the event handler.

        @warn: This is normally not needed. Use with care!

        @type  eventHandler: L{EventHandler}
        @param eventHandler: New event handler object, or C{None}.

        @rtype:  L{EventHandler}
        @return: Previous event handler object, or C{None}.

        @raise TypeError: The event handler is of an incorrect type.

        @note: The L{eventHandler} parameter may be any callable Python object
            (for example a function, or an instance method).
            However you'll probably find it more convenient to use an instance
            of a subclass of L{EventHandler} here.