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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 save_networkfile(self, filepath: Union[str, None] = None, write_nodes: bool = True) -> None: """Save the selection as a network file. In most cases, one should conveniently write network files via method |NetworkManager.save_files| of class |NetworkManager|. However, using the method |Selection.save_networkfile| allows for additional configuration via the arguments `filepath` and `write_nodes`: # -*- coding: utf-8 -*- <BLANKLINE> from hydpy import Node, Element <BLANKLINE> <BLANKLINE> Node("dill", variable="Q", keywords="gauge") <BLANKLINE> Node("lahn_1", variable="Q", keywords="gauge") <BLANKLINE> <BLANKLINE> Element("land_dill", outlets="dill", keywords="catchment") <BLANKLINE> Element("land_lahn_1", outlets="lahn_1", keywords="catchment") <BLANKLINE> # -*- coding: utf-8 -*- <BLANKLINE> from hydpy import Node, Element <BLANKLINE> <BLANKLINE> Element("land_dill", outlets="dill", keywords="catchment") <BLANKLINE> Element("land_lahn_1", outlets="lahn_1", keywords="catchment") <BLANKLINE> """

        if filepath is None:
            filepath = self.name + '.py'
        with open(filepath, 'w', encoding="utf-8") as file_:
            file_.write('# -*- coding: utf-8 -*-\n')
            file_.write('\nfrom hydpy import Node, Element\n\n')
            if write_nodes:
                for node in self.nodes:
                    file_.write('\n' + repr(node) + '\n')
                file_.write('\n')
            for element in self.elements:
                file_.write('\n' + repr(element) + '\n')