'Backend derived classes should call this function on any mouse
button release.
This method will call all functions connected to the
\'button_release_event\' with a :class:`MouseEvent` instance.
Parameters
x : scalar
the canvas coordinates where 0=left
y : scalar
the canvas coordinates where 0=bottom
guiEvent
the native UI event that generated the mpl event'

def button_release_event(self, x, y, button, guiEvent=None):

    s = u'button_release_event'
    event = MouseEvent(s, self, x, y, button, self._key, guiEvent=guiEvent)
    self.callbacks.process(s, event)
    self._button = None
