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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 get_version(self, version_id=None):
 """Return specific version ``ObjectVersion`` instance or HEAD. :param version_id: Version ID of the object. :returns: :class:`~invenio_files_rest.models.ObjectVersion` instance or HEAD of the stored object. """

        return ObjectVersion.get(bucket=self.obj.bucket, key=self.obj.key,
                                 version_id=version_id)