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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 collect_variables(self, selections) -> None: """Apply method |ExchangeItem.insert_variables| to collect the relevant target variables handled by the devices of the given |Selections| object. We prepare the `LahnH` example project to be able to use its |Selections| object: We change the type of a specific application model to the type of its base model for reasons explained later: We prepare a |SetItem| as an example, handling all |hland_states.Ic| sequences corresponding to any application models derived from |hland|: ExchangeSpecification('hland', 'states.ic') Applying method |ExchangeItem.collect_variables| connects the |SetItem| object with all four relevant |hland_states.Ic| objects: True land_dill land_lahn_1 land_lahn_2 land_lahn_3 Asking for |hland_states.Ic| objects corresponding to application model |hland_v1| only, results in skipping the |Element| `land_lahn_3` (handling the |hland| base model due to the hack above):
 land_dill land_lahn_1 land_lahn_2 Selecting a series of a variable instead of the variable itself only affects the `targetspec` attribute: ExchangeSpecification('hland_v1', 'inputs.t.series') True It is both possible to address sequences of |Node| objects, as well as their time series, by arguments "node" and "nodes": ExchangeSpecification('node', 'sim') True dill lahn_1 lahn_2 lahn_3 ExchangeSpecification('nodes', 'sim.series') dill lahn_1 lahn_2 lahn_3 """

        self.insert_variables(self.device2target, self.targetspecs, selections)