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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 _unpack_case(self, case):
 """ Returns the contents of the case to be used in the OPF. """

        base_mva = case.base_mva
        b = case.connected_buses
        l = case.online_branches
        g = case.online_generators
        nb = len(b)
        nl = len(l)
        ng = len(g)

        return b, l, g, nb, nl, ng, base_mva