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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 _var_bounds(self):
 """ Returns bounds on the optimisation variables. """

        x0 = array([])
        xmin = array([])
        xmax = array([])

        for var in self.om.vars:
            x0 = r_[x0, var.v0]
            xmin = r_[xmin, var.vl]
            xmax = r_[xmax, var.vu]

        return x0, xmin, xmax