def _set_preview_alpha(self, value):
    self._check_camera_open()
    warnings.warn(PiCameraDeprecated('PiCamera.preview_alpha is deprecated; use PiCamera.preview.alpha instead'))
    if self.preview:
        self.preview.alpha = value
    else:
        self._preview_alpha = value
def _set_preview_alpha(self, value):
    self._check_camera_open()
    warnings.warn(PiCameraDeprecated('PiCamera.preview_alpha is deprecated; use PiCamera.preview.alpha instead'))
    if self.preview:
        self.preview.alpha = value
    else:
        self._preview_alpha = value