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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 get_xy(self, yidx, xidx=0):
 """ Return stored data for the given indices for plot :param yidx: the indices of the y-axis variables(1-indexing) :param xidx: the index of the x-axis variables :return: None """

        assert isinstance(xidx, int)
        if isinstance(yidx, int):
            yidx = [yidx]

        t_vars = self.concat_t_vars()

        xdata = t_vars[:, xidx]
        ydata = t_vars[:, yidx]

        return xdata.tolist(), ydata.transpose().tolist()