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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 export_model(self, export_formats, export_dir=None):
 """Exports model based on export_formats. Subclasses should override _export_model() to actually export model to local directory. Args: export_formats (list):
 List of formats that should be exported. export_dir (str):
 Optional dir to place the exported model. Defaults to self.logdir. Return: A dict that maps ExportFormats to successfully exported models. """

        export_dir = export_dir or self.logdir
        return self._export_model(export_formats, export_dir)