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.

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)