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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def isChanged(self, min_changed_pixels, screen_state):
 """ Returns true if at least ``min_changed_pixels`` are different between ``screen_state`` and the current state. """

        r = self.clipRegionToScreen()
        current_state = r.getBitmap()
        diff = numpy.subtract(current_state, screen_state)
        return (numpy.count_nonzero(diff) >= min_changed_pixels)