last change of keyboard state occurred while the canvas did not have
           focus, this attribute will be wrong.  On the other hand, the
           ``modifiers`` attribute should always be correct, but it can only
           report on modifier keys.

    step : float
        The number of scroll steps (positive for 'up', negative for 'down').
        This applies only to 'scroll_event' and defaults to 0 otherwise.

    dblclick : bool
        Whether the event is a double-click. This applies only to
        'button_press_event' and is False otherwise. In particular, it's
        not used in 'button_release_event'.

    Examples
    --------
    ::

        def on_press(event):
            print('you pressed', event.button, event.xdata, event.ydata)

        cid = fig.canvas.mpl_connect('button_press_event', on_press)
    Nr