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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 y0(self):
 """Y-axis coordinate of the first data point :type: `~astropy.units.Quantity` scalar """

        try:
            return self._y0
        except AttributeError:
            self._y0 = Quantity(0, self.yunit)
            return self._y0