def setAlpha(self, alpha):
    if ((alpha < 0) or (alpha > 1)):
        raise ValueError('alpha must be in between 0 and 1')
    self._alpha = alpha
def setAlpha(self, alpha):
    if ((alpha < 0) or (alpha > 1)):
        raise ValueError('alpha must be in between 0 and 1')
    self._alpha = alpha