def __init__(self, widget, *tks):
self._widget = widget<EOL>self._tks = tks<EOL>self._refs = {}<EOL>self._event_callbacks = {}<EOL>
The EventManager handles all the events and callbacks for a guizero
widget.

Every event created must be given a reference, this reference
is how events are managed internally within guizero.

A guizero widget can contain many tk widgets, so all the tk objects
for this guizero widget need to passed.