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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 limit_x( self, limit_lower = None, # float limit_upper = None # float ):
 """ get or set x limits of the current axes x_min, x_max = limit_x() # return the current limit_x limit_x(x_min, x_max) # set the limit_x to x_min, x_max """


        if limit_lower is None and limit_upper is None:
            return self._limit_x
        elif hasattr(limit_lower, "__iter__"):
            self._limit_x = limit_lower[:2]
        else:
            self._limit_x = [limit_lower, limit_upper]
        if self._limit_x[0] == self._limit_x[1]:
            self._limit_x[1] += 1
        self._limit_x[0] -= self.mod_x
        self._limit_x[1] += self.mod_x