Original uploaded data file the subject was created from.

        Returns
        -------
        File-type object
            Reference to file on local disk

def data_file(self):
        """Original uploaded data file the subject was created from.

        Returns
        -------
        File-type object
            Reference to file on local disk
        """
        return os.path.join(self.upload_directory, self.properties[datastore.PROPERTY_FILENAME])