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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 _prepare_wsdl_objects(self):
 """ This sets the package identifier information. This may be a tracking number or a few different things as per the Fedex spec. """


        self.SelectionDetails = self.client.factory.create('TrackSelectionDetail')

        # Default to Fedex
        self.SelectionDetails.CarrierCode = 'FDXE'

        track_package_id = self.client.factory.create('TrackPackageIdentifier')

        # Default to tracking number.
        track_package_id.Type = 'TRACKING_NUMBER_OR_DOORTAG'

        self.SelectionDetails.PackageIdentifier = track_package_id