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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 _structmap(self):
 """ Returns structMap element for all files. """

        structmap = etree.Element(
            utils.lxmlns("mets") + "structMap",
            TYPE="physical",
            # TODO Add ability for multiple structMaps
            ID="structMap_1",
            # TODO don't hardcode this
            LABEL="Archivematica default",
        )
        for item in self._root_elements:
            child = item.serialize_structmap(recurse=True)
            if child is not None:
                structmap.append(child)

        return structmap