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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_model(self, fname, include_unsigned_edges=False):
 """Save the assembled model's SIF string into a file. Parameters fname : str The name of the file to save the SIF into. include_unsigned_edges : bool If True, includes edges with an unknown activating/inactivating relationship (e.g., most PTMs). Default is False. """

        sif_str = self.print_model(include_unsigned_edges)
        with open(fname, 'wb') as fh:
            fh.write(sif_str.encode('utf-8'))