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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 zoom_in(self):
 """Scale the image up by one scale step."""

        if self._scalefactor <= self._sfmax:
            self._scalefactor += 1
            self.scale_image()
            self._adjust_scrollbar(self._scalestep)
            self.sig_zoom_changed.emit(self.get_scaling())