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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 close_boundaries_sensibly(model):
 """ Return a cobra model with all boundaries closed and changed constraints. In the returned model previously fixed reactions are no longer constrained as such. Instead reactions are constrained according to their reversibility. This is to prevent the FBA from becoming infeasible when trying to solve a model with closed exchanges and one fixed reaction. Parameters model : cobra.Model The metabolic model under investigation. Returns ------- cobra.Model A cobra model with all boundary reactions closed and the constraints of each reaction set according to their reversibility. """

    for rxn in model.reactions:
        if rxn.reversibility:
            rxn.bounds = -1, 1
        else:
            rxn.bounds = 0, 1
    for boundary in model.boundary:
        boundary.bounds = (0, 0)