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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 reverse_axis(self, axis_to_reverse):
 """Reverse an axis in all figure plots. This will reverse the tick marks on an axis for each plot in the figure. It can be overridden in SinglePlot class. Args: axis_to_reverse (str):
 Axis to reverse. Supports `x` and `y`. Raises: ValueError: The string representing the axis to reverse is not `x` or `y`. """

        if axis_to_reverse.lower() == 'x':
            self.general.reverse_x_axis = True
        if axis_to_reverse.lower() == 'y':
            self.general.reverse_y_axis = True
        if axis_to_reverse.lower() != 'x' or axis_to_reverse.lower() != 'y':
            raise ValueError('Axis for reversing needs to be either x or y.')
        return