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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 _createGaVariantAnnotation(self):
 """ Convenience method to set the common fields in a GA VariantAnnotation object from this variant set. """

        ret = protocol.VariantAnnotation()
        ret.created = self._creationTime
        ret.variant_annotation_set_id = self.getId()
        return ret